Enzymes are biological catalysts that facilitate biochemical reactions in horses by lowering the activation energy required for these processes. They are involved in various physiological functions, including digestion, metabolism, and cellular repair. Common enzymes in equine biology include amylase, lipase, and lactate dehydrogenase, each playing a specific role in the breakdown of nutrients and energy production. The activity and concentration of these enzymes can vary in response to different physiological and pathological conditions, serving as potential indicators in veterinary diagnostics. This page compiles peer-reviewed research studies and scholarly articles that explore the function, regulation, and clinical implications of enzymes in equine health.
Hildebrand DP, Burk DL, Maurus R, Ferrer JC, Brayer GD, Mauk AG.The spectroscopic and structural properties of the His93Tyr variant of horse heart myoglobin have been studied to assess the effects of replacing the proximal His residue of this protein with a tyrosyl residue as occurs in catalases from various sources. The variant in the ferric form exhibits electronic spectra that are independent of pH between pH 7 and 10, and it exhibits changes in absorption maxima and intensity that are consistent with a five-coordinate heme iron center at the active site. The EPR spectrum of the variant is that of a high-spin, rhombic system similar to that reported for...
Nishita T, Ohohashi T, Asari M.The concentration of carbonic anhydrase III isoenzyme (CA-III) in serum samples from 216 clinically normal Thoroughbreds was determined by use of an enzyme immunoassay. The concentration range of CA-III was from 16.0 to 254.5 ng/ml (mean, 56.5 +/- 11.9 ng/ml). Significant differences were not detected according to age or sex. To confirm whether serum CA-III concentration was high in horses with muscle disease, serum samples of 11 horses with exertional rhabdomyolysis were analyzed by enzyme immunoassay. Their serum CA-III concentration was about 56 times (3,136 +/- 2,610 ng/ml) that of healthy...
Jasińska B.The degree of proteolysis of micellar caseins of human, goat's, mare's and two breeds (Black&White and Red Polish) of cow's milk was compared for pepsin and trypsin action in vitro. Human and goat's caseins were hydrolysed in 100% and 96%, respectively, mare's casein--92%, Black&White cow's casein--90%, Red Polish cow's casein--76%. The differences can be related to the micelle structure, especially to the prevalence of beta casein in the human and goat's casein. The significant dissimilarity between the two breeds of investigated cows is surprising and indicates a different geometry o...
Avellini L, Silvestrelli M, Gaiti A.Oxidative stress develops when the generation of free radicals exceeds the antioxidant capacity of cells or extracellular fluids. It can also occur as a result of physical exercise, and the pathogenesis of exercise-induced myopathies and haemolysis in horses may be related to changes in lipid peroxidation caused by free radicals. Cells have developed biochemical protection against oxidative stress and, as tissues seem to increase their antioxidant defences under chronic activation, training may be one of the ways of increasing antioxidant defences. Accordingly, we tested some enzymatic antioxi...
Sandholm M, Vidovic A, Puotunen-Reinert A, Sankari S, Nyholm K, Rita H.The discriminating ability of 15 parameters alone or in combinations, including results from analysis of plasma endotoxin, the Nycomed plasma D-Dimer test and phospholipase A2, were analyzed to predict morbidity and mortality in equine gastrointestinal colic. Endotoxaemia was a characteristic feature of the colic horses. The problem of adequately predicting nonsurvivors among colic horses required several parameters to be included in the logistic model: if the "classical parameters", (heart rate, respiratory rate, PCV, anion gap) were included in the model, addition of plasma D-dimer, phosphol...
Gibson JS, Hall AC.The effects of hydrostatic pressure on the KCl co-transporter of equine erythrocytes were studied to determine factors involved in its regulation. Pressure (0.1-40MPa) increased Cl-dependent K+ transport; in the presence of the putative kinase inhibitor N-ethylmaleimide (NEM) which stimulates the transporter, or the phosphatase inhibitor calyculin A, pressure had no significant effect. The sequential application of NEM and calyculin A clamped the transporter at about 30% of maximal flux compared to NEM alone; pressure also had no further effect. These results suggest that pressure acts on the ...
Ichinose T, Miller MG, Shibamoto T.Free malonaldehyde formed in the microsomes prepared from livers of monkey, rat, rabbit, mouse, cow, pig, dog, sheep and horse upon CCl4 oxidation was derivatized by reaction with N-methylhydrazine to form 1-methylpyrazole which was subsequently analyzed by capillary gas chromatography. Among the livers from animals tested, the monkey and rat livers produced the most malonaldehyde upon CCl4 treatment. Horse liver showed the greatest resistance to CCl4 oxidation. The gas chromatography method used in the present study exhibited an accurate and specific measurement of free malonaldehyde that mig...
Collatos C, Barton MH, Schleef R, Prasse KW, Moore JN.Much of the pathophysiology associated with equine gastrointestinal diseases is attributed to the effects of endotoxin on haemostasis. Because little is known about the responses of the equine fibrinolytic system to endotoxin, regulation of the system was investigated. Tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1) were identified as the primary plasminogen activator and plasminogen activator inhibitor, respectively, in equine blood. Under experimental conditions, the equine fibrinolytic system responded to endotoxin in a manner similar to that repo...
Taddei N, Buck M, Broadhurst RW, Stefani M, Ramponi G, Dobson CM.The stability and equilibrium unfolding behaviour of horse muscle acylphosphatase have been studied by denaturing the protein under various conditions of temperature, pH, and urea concentration. Far-ultraviolet circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopy indicate that this small monomeric protein unfolds reversibly and cooperatively. Thermodynamic parameters, the Gibbs free energy delta G and enthalpy delta H of unfolding, have been estimated for denaturation of the protein from NMR and CD data as 19 kJ mol-1 and 350 kJ mol-1, respectively. CD and 1H-NMR results s...
Nikiforov TT, Rendle RB, Goelet P, Rogers YH, Kotewicz ML, Anderson S, Trainor GL, Knapp MR.A new method for typing single nucleotide polymorphisms in DNA is described. In this method, specific fragments of genomic DNA containing the polymorphic site(s) are first amplified by the polymerase chain reaction (PCR) using one regular and one phosphorothioate-modified primer. The double-stranded PCR product is rendered single-stranded by treatment with the enzyme T7 gene 6 exonuclease, and captured onto individual wells of a 96 well polystyrene plate by hybridization to an immobilized oligonucleotide primer. This primer is designed to hybridize to the single-stranded target DNA immediately...
Schmid A, Schmid H.In this paper, the metabolism of xenobiotics in the horse, including differences to other species, is discussed. The most important metabolic reactions of phase I (oxidation, reduction and hydrolysis of substrates), as well as of phase II (conjugation of substrates with glucuronic acid, sulphuric acid, acetic acid, alkyl groups, amino acids, amino acid derivatives, glutathione etc.), are discussed and enzymes involved in the metabolic reactions are considered.
Maisi P, Koivunen AL, Rantala AR, Turgut K.The health of the respiratory tracts of 19 horses was studied for 11 months. The horses were placed into 3 groups (healthy, periodically diseased and continuously diseased) based on the measurements of blood gases, intrapleural pressure and on neutrophil content of tracheal mucus. Lysosomal enzymes (N-acetyl-beta-D-glucosaminidase and beta-glucuronidase) and reflectors of the proteolytic system (plasmin, plasminogen, trypsin inhibitor capacity) were determined. beta-glucuronidase appeared to be a good indicator of the presence of disease of the respiratory system. High beta-glucuronidase value...
Snijder EJ, Wassenaar AL, Spaan WJ.To study the proteolytic processing of the equine arteritis virus (EAV) replicase open reading frame 1a (ORF1a) protein, specific antisera were raised in rabbits, with six synthetic peptides and a bacterial fusion protein as antigens. The processing of the EAV ORF1a product in infected cells was analyzed with Western blot (immunoblot) and immunoprecipitation techniques. Additional information was obtained from transient expression of ORF1a cDNA constructs. The 187-kDa ORF1a protein was found to be subject to at least five proteolytic cleavages. The processing scheme, which covers the entire OR...
Milne EM, Pemberton AD, McGorum BC, Dixon PM, Miller HR.The equine alpha-1 proteinase inhibitor (alpha 1PI) system differs from that of man in that the equine system consists of four closely-linked genes (Spi1-Spi4) whereas in man, a single gene encodes for alpha 1PI. We have previously found differences in the proportion of the Spi proteins in equine serum and bronchoalveolar lavage fluid (BALF). We therefore wished to determine whether, as reported in man, there was any molecular weight difference between the Spi proteins in serum and BALF. alpha 1PI and albumin from equine BALF migrated further towards the anode compared with serum alpha 1PI on ...
Wilkins PA, Ducharme NG, Lowe JE, Schwark WS, Meschter C, Erb HN.To assess right colic artery blood flow and relevance of xanthine dehydrogenase/xanthine oxidase after experimentally induced strangulation obstruction and reperfusion of the colon, 5 ponies were subjected to 2.5 hours of complete ischemia of the left dorsal and ventral colons, allowed to recover from surgery, and monitored during a 48-hour reperfusion period. Five ponies were subjected to sham surgery and served as controls. All ponies had a Doppler ultrasound blood flow monitor implanted on the right colic artery near the pelvic flexure 10 to 14 days prior to the ischemic period. Colic arter...
Palma F, Ligi F, Soverchia C.This work is a comparative study of Na(+)-K+ and Ca(2+)-Mg2+ ATPase associated with the erythrocyte plasma membranes in different mammals. The method used to test the activity of these enzymes is based on quantitative measurements of ADP released during the reaction with HPLC: the chromatographic type is an Ion-Pair Reversed Phase. We have found that the levels of Ca2+ stimulated ATPase are higher than those of Na(+)-K+ ATPase in red blood cells of all the different mammalian species, with the only exception being lamb erythrocytes where the values of both the ATPase activities are almost equa...
Eisenhauer KM, McCue PM, Nayden DK, Osawa Y, Roser JF.Stallion testes secrete large amounts of estrogens, but the cellular location of the enzyme that converts androgens to estrogens, cytochrome P450 aromatase, has not been determined. The goal of the present study was to immunocytochemically localize stallion testicular aromatase using a polyclonal antibody generated against human placental cytochrome P450 aromatase. Testes were obtained from 12 stallions from 2 to 23 years of age, during both the breeding and non-breeding seasons. Immunoreactivity was confined to the Leydig cells in all testes examined. No immunostaining was observed in the Ser...
Miles CA, Wardale RJ, Birch HL, Bailey AJ.Differential scanning calorimetry (DSC) of equine superficial digital flexor tendons revealed the presence of a small exothermic peak at 23 degrees C of unknown origin, and a large endothermic peak at 70 degrees C due to denaturation of cross-linked collagen fibres. In the central degenerated core of damaged tendons the denaturation temperature remained at 70 degrees C but the enthalpy decreased in relation to the extent of degeneration of the tendon. We suggest that this reduction in enthalpy is due to depolymerisation and denaturation of the collagen fibres. This contention is supported by t...
Ronéus M, Persson SG, Essén-Gustavsson B, Arnason T.Muscle biopsy specimens from the middle gluteal muscle were studied in 16 red blood cell hypervolaemic (Group HV) and 19 normovolaemic (Group NV) Standardbred racehorses. All horses were stallions, 4-8 years old and having similar mean racing performance values, as described by an individual selection index value. All horses raced regularly but those in Group HV did not perform as expected and were therefore referred to the clinics for exercise tolerance testing. Muscle biopsy specimens were analysed for fibre type distribution (Type I, IIA and IIB), fibre area and relative fibre area. In addi...
Pirhonen A, Linnala-Kankkunen A, Mënpää PH.P1 protamines isolated from ejaculated human, stallion, bull, boar and ram spermatozoa and P2 protamines from human and stallion spermatozoa were subjected, after alkaline phosphatase treatment, to in vitro phosphorylation reactions using cAMP-dependent protein kinase (PKA) and protein kinase C (PKC). All P1 protamines were phosphorylated by PKA, whereas P2 protamines were phosphorylated only by PKC. In addition, human, stallion and boar, but not bull and ram, P1 protamines were phosphorylated by PKC. After phosphoamino acid analysis, the protamines showing positive signals for phosphoserine (...
Bell K.Transferrin, albumin, 6-phosphogluconate dehydrogenase and vitamin D-binding protein polymorphisms were detected in 242 feral and domesticated Australian donkeys by polyacrylamide gel electrophoresis, starch gel electrophoresis, autoradiography, immunoblotting with specific antisera and activity staining. All four TF and two ALB variants were donkey specific while only one of the PGD variants was donkey specific. The two GC variants were electrophoretically identical to the Equus caballus F and S proteins. Available evidence suggested that the TF, ALB, PGD and GC systems are controlled by co-d...
Dubin A, Potempa J, Travis J.In order better to understand the pathophysiology of the equine form of emphysema, two elastinolytic enzymes from horse neutrophils, referred to as proteinases 2A and 2B, have been extensively characterized and compared with the human neutrophil proteinases, proteinase-3 and elastase. Specificity studies using both the oxidized insulin B-chain and synthetic peptides revealed that cleavage of peptide bonds with P1 alanine or valine residues was preferred. Further characterization of the two horse elastases by N-terminal sequence and reactive-site analyses indicated that proteinases 2A and 2B ha...
Lees P, McKellar Q, May SA, Ludwig B.The pharmacokinetics and pharmacodynamics of the nonsteroidal anti-inflammatory drug (NSAID) carprofen have been evaluated in 6 horses using a model of acute non-immune inflammation. Following intravenous administration of 0.7 mg racemic carprofen/kg bwt, mean values for pharmacokinetic parameters were 18.1 h (elimination half-life); 0.25 l/kg (volume of distribution, Vd[area]); 58.9 ml/min (clearance); and 57.9 micrograms/ml.h (area under plasma concentration time curve). Mean exudate:plasma concentration ratios exceeded 1.0 at all sampling times between 2 and 48 h. Swelling at the site of ac...
Sewell DA, Harris RC, Marlin DJ.Skeletal muscle samples were obtained by needle biopsy from two depths of the m. gluteus medius of 50, young race-trained thoroughbred racehorses. Histochemical and biochemical characteristics of the muscle samples were analysed. Fibres were classified as type I, type IIa or type IIb on the basis of the pH dependent lability of the myosin ATPase reaction. The activities of citrate synthase (CS) and glycogen phosphorylase (Phos) were determined. Muscle fibre composition varied markedly between deep and superficial muscle samples and this was reflected in differences in the activities of citrate...
Agmon N, Doster W, Post F.Heme proteins react inhomogeneously with ligands at cryogenic temperatures and homogeneously at room temperature. We have identified and characterized a transition from inhomogeneous to homogeneous behavior at intermediate temperatures in the time dependence of CO binding to horse myoglobin. The turnover is attributed to a functionally important tertiary protein relaxation process during which the barrier increases dynamically. This is verified by a combination of theory and multipulse measurements. A likely biological significance of this effect is in the autocatalysis of the ligand release p...
Ko WH, O'Dowd JJ, Pediani JD, Bovell DL, Elder HY, Jenkinson DM, Wilson SM.Changes in intracellular free calcium concentration ([Ca2+]i) were monitored in a cell line that was derived from the equine sweat gland epithelium. ATP and closely related compounds could increase [Ca2+]i with a rank order of potency of UTP > or = ATP > ADP >> AMP = adenosine = alpha,beta-methylene-ATP. The responses to ATP and to UTP were initiated by the release of calcium from an internal store and subsequently sustained by calcium influx. The rise in [Ca2+]i thus seems to be mediated by P2U receptors that are coupled to phosphoinositidase C. Some desensitisation of this respon...
Hough SR, Parks JE.Platelet-activating factor (PAF) acetylhydrolase, which inactivates PAF, has been detected in human and bovine seminal plasma and may represent a mechanism for regulating sperm-derived PAF. This study was designed to characterize further PAF acetylhydrolase in seminal plasma from domestic animal species. Sperm-free seminal plasma from the bull, stallion, rabbit, and rooster was assayed for acetylhydrolase activity based on the release of [3H]acetate from PAF. As reported previously for bull seminal plasma, activity in stallion, rabbit, and rooster seminal plasma was linear with both time and p...
Plumlee KH, Richardson ER, Gardner IA, Galey FD.Delays between time of sampling and time of testing are common; therefore, the length of time that blood can be stored at various temperatures was evaluated for effects on cholinesterase activity. Six horses were treated with 16 g of trichlorfon per os, 6 horses were treated with 15 g of dichlorvos per os, and 10 horses were untreated controls. The cholinesterase activity in whole blood from each horse was measured using an adaptation of the Ellman colorimetric method. The blood from each horse was then divided into 3 groups and stored at 5 C (refrigerated), 20 C (room temperature), or 38 C (i...
Singh B, Minhas KJ, Atwal OS.The pulmonary intravascular macrophages (PIMs) of the ponies possess all the characteristics of a fully differentiated resident macrophage, which forms adhesive plaques with the capillary-endothelial cells. In addition, it has a unique surface coat which does not conform to the concept of a carbohydrate rich membrane bound glycocalyx generally associated with macrophages. We studied the responses of these cells especially in the context of its globular surface coat to multiple doses of MB intravenously: 0.2 ml/kg body copper tracer substance. The ponies were treated with three doses of MB intr...
Caffrey CR, Ryan MF.An excretory-secretory (ES) preparation derived from adult Strongylus vulgaris in vitro was assessed for proteolytic activity using azocasein and synthetic, fluorogenic, peptide substrates. Fractionation was by molecular sieve fast protein liquid chromatography (molecular sieve FPLC) and resolution by gelatin-substrate sodium dodecyl sulphate-polyacrylamide gel electrophoresis (gelatin-substrate SDS-PAGE). The cysteine proteinase activator, dithiothreitol (DTT), enhanced azocaseinolysis and hydrolysis of carbobenzoxy-phenylalanyl-arginine-7-amido-4-methylcoumarin (Z-Phe-Arg-NMec) by the ES pre...
Carmichael SW, Weber A, Winkler H.The uptake of nucleotides and catecholamines into chromaffin granules from adrenals of pigs and horses is similar to that previously seen in bovine chromaffin granules. The rate of [3H]ATP uptake at 2 mM-ATP concentration was 0.42 +/- 0.06 and 0.15 +/- 0.02 nmol/mg protein/min for pig and horse granules, respectively. The apparent Km's were 1.37 mM for pig granules, 0.89 mM for horse granules, and 1.2 mM for ox granules. The sensitivity of the uptake for nucleotides and catecholamine to specific inhibitors was found to be similar in granules from pig and ox, indicating that the same mechanisms...
Stokol T, Erb H.We investigated the apo-enzyme content of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in clinically normal and ill canine, feline, equine and bovine patients. Aminotransferase activity was measured with and without the addition of exogenous pyridoxal-5'-phosphate (P5P). The amount of apo-enzyme was expressed as the percentage change in aminotransferase activity with the inclusion of P5P. The results of aminotransferase assays without P5P (holo-enzyme activity) were highly correlated to the results obtained with P5P (total enzyme activity) in all four species (Spearman r...
Patterson WH, Brown CM.Serial blood samples were obtained from 16 Standardbred foals from time of birth to postpartum day 28. Sera were obtained and analyzed for gamma-glutamyltransferase (GGT), aspartate transaminase, and immunoglobulin (Ig) G. Presuckle colostrum from the respective mares of these foals was analyzed for GGT activity. Mean serum aspartate transaminase activities were significantly increased above presuckle values by postpartum hour 48 (P less than 0.01) and increased gradually over the first 14 days. Mean serum IgG concentrations were significantly greater than presuckle values by 5 hours after foa...
Poole DC, Petrisko RN, Anderson L, Fedde MR, Erickson HH.During exercise, the horse can achieve oxygen uptakes and ventilations in excess of 200 ml/kg/min and 1800 l/min, respectively. Whether the diaphragm has the capacity to contribute substantially to inspiratory effort in the exercising horse is not known. To investigate the potential for the horse diaphragm to generate tension, lung displacement and sustain ventilatory function, we measured diaphragm thickness, muscle length and oxidative enzyme activity (citrate synthase) within the ventral, medial and dorsal costal and crural diaphragm. In the diaphragms of 6 mature horses (5 Thoroughbreds, o...
Yamamoto M, Tanaka Y, Sugano M.1. The lipid composition of serum and liver and some properties of serum lecithin: cholesterol acyltransferase of the horse were investigated. 2. Phospholipids and cholesterol were the major components of serum lipids and the concentration of triglyceride was considerably low. The concentration of liver lipids was comparable with that of other mammals. 3. Fatty acid composition of serum cholesterol ester resembled that of the 2-position of lecithin, except palmitic acid. 4. The activity of serum cholesterol esterifying enzyme was found to be 0.03-0.09 mumol/hr per ml. There was an equimolar de...
Nishita T, Ohohashi T, Asari M.The concentration of carbonic anhydrase III isoenzyme (CA-III) in serum samples from 216 clinically normal Thoroughbreds was determined by use of an enzyme immunoassay. The concentration range of CA-III was from 16.0 to 254.5 ng/ml (mean, 56.5 +/- 11.9 ng/ml). Significant differences were not detected according to age or sex. To confirm whether serum CA-III concentration was high in horses with muscle disease, serum samples of 11 horses with exertional rhabdomyolysis were analyzed by enzyme immunoassay. Their serum CA-III concentration was about 56 times (3,136 +/- 2,610 ng/ml) that of healthy...
Martini F, Angelaccio S, Barra D, Doonan S, Bossa F.Cytosolic aspartate aminotransferase (L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1) from horse heart has five cysteine residues, two of which can be titrated with 5,5'-dithiobis(2-nitrobenzoid acid) in the native enzyme with no impairment of catalytic activity. The rate of modification is unaffected by the presence of substrates. Reaction with N-ethylmaleimide leads to loss of catalytic activity, the rate of inactivation being increased by the presence of substrates. Peptides containing 361 amino-acid residues (about 88% of the total number in the protein) have been isolated and ali...
Sonea IM, Bowker RM, Robinson NE, Broadstone RV.Immunohistochemical methods were used to determine the distribution of pulmonary nerves containing either an enzymatic marker of adrenergic nerves, dopamine beta hydroxylase, or the putative neurotransmitter neuropeptide Y in 7 equids with healthy lungs. Nerves immunoreactive for these substances were found on airway smooth muscle in nearly all the samples of healthy equine lung examined. These nerves were generally more numerous in the larger airways but could be detected even in noncartilaginous bronchioles. Pulmonary and bronchial vessels also contained numerous immunoreactive nerves. On th...
Burns TA, Watts MR, Weber PS, McCutcheon LJ, Geor RJ, Belknap JK.In EMS-associated laminitis, laminar failure may occur in response to energy failure related to insulin resistance (IR) or to the effect of hyperinsulinemia on laminar tissue. 5'-Adenosine-monophosphate-activated protein kinase (AMPK) is a marker of tissue energy deprivation, which may occur in IR. Objective: To characterize tissue AMPK regulation in ponies subjected to a dietary carbohydrate (CHO) challenge. Methods: Twenty-two mixed-breed ponies. Methods: Immunohistochemistry and immunoblotting for total AMPK and phospho(P)-AMPK and RT-qPCR for AMPK-responsive genes were performed on laminar...
Autry JM, Svensson B, Carlson SF, Chen Z, Cornea RL, Thomas DD, Valberg SJ.We have analyzed the enzymatic activity of the sarcoplasmic reticulum (SR) Ca2+-transporting ATPase (SERCA) from the horse gluteal muscle. Horses are bred for peak athletic performance yet exhibit a high incidence of exertional rhabdomyolysis, with elevated levels of cytosolic Ca2+ proposed as a correlative linkage. We recently reported an improved protocol for isolating SR vesicles from horse muscle; these horse SR vesicles contain an abundant level of SERCA and only trace-levels of sarcolipin (SLN), the inhibitory peptide subunit of SERCA in mammalian fast-twitch skeletal muscle. Here, we re...
Hamilton NA, Tammen I, Raadsma HW.Angiotensin converting enzyme (ACE) is essential for control of blood pressure. The human ACE gene contains an intronic Alu indel (I/D) polymorphism that has been associated with variation in serum enzyme levels, although the functional mechanism has not been identified. The polymorphism has also been associated with cardiovascular disease, type II diabetes, renal disease and elite athleticism. We have characterized the ACE gene in horses of breeds selected for differing physical abilities. The equine gene has a similar structure to that of all known mammalian ACE genes. Nine common single nuc...
Jackson B, Eastell R, Russell RG, Lanyon LE, Price JS.For many years total alkaline phosphatase (AP) activity in serum has been used to monitor bone metabolism in different species. However, total AP lacks bone specificity because the total activity in serum is made up of several isoenzymes, of which the liver and bone isoforms predominate. The aim of the present study was to evaluate an immunoradiometric assay for measuring bone specific alkaline phosphatase (BAP) in horses. BAP, a specific marker of bone formation, was measured in sera from thoroughbred horses by using a previously characterised wheat germ lectin (WGL) precipitation assay and a...
Ronéus M, Persson SG, Essén-Gustavsson B, Arnason T.Muscle biopsy specimens from the middle gluteal muscle were studied in 16 red blood cell hypervolaemic (Group HV) and 19 normovolaemic (Group NV) Standardbred racehorses. All horses were stallions, 4-8 years old and having similar mean racing performance values, as described by an individual selection index value. All horses raced regularly but those in Group HV did not perform as expected and were therefore referred to the clinics for exercise tolerance testing. Muscle biopsy specimens were analysed for fibre type distribution (Type I, IIA and IIB), fibre area and relative fibre area. In addi...
Wang L, Unger L, Sharif H, Eriksson S, Gerber V, Rönnberg H.Thymidine kinase 1 (TK1) plays a key role in the synthesis of deoxythymidine triphosphate (dTTP) and is thus important for DNA replication and cell proliferation. The expression of TK1 is highest during S-phase, and it is rapidly degraded after mitosis. In cancer cells, TK1 is upregulated, resulting in leakage of excess TK1 into the blood. Consequently, serum TK1 has been used as a diagnostic and prognostic cancer biomarker, mainly in human medicine. The aims of this work were to characterize equine TK1 and to evaluate its suitability as a serum biomarker for equine lymphoma. Results: Equine T...
Varhac R, Antalík M.A relation between pH-induced conformational transitions of horse heart ferricytochrome c and the kinetics of external ligand coordination to heme iron was investigated by optical spectroscopy, circular dichroism and viscometry. The dependencies of both the association, k (a), and dissociation rate constants of cyanide binding on pH were determined from kinetic measurements. The association rate constant exhibits a bell-shaped form of dependence on pH in the region where this protein unfolds. The maximum of the dependence of k (a) on pH is found to be coincident with the pK values of conformat...
Farley J, Sirois J, MacFarlane PH, Kombé A, Laverty S.To characterize expression of cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) and regulation of prostaglandin E2 (PGE2) production by equine articular chondrocytes. Methods: Articular cartilage from the metacarpophalangeal joints of 7 adult horses. Methods: Equine chondrocyte monolayer cultures were stimulated with different concentrations (2.5, 5, 10, and 20 ng/mL) of recombinant human interleukin-1beta (rhIL-1beta) for 24 hours and then with rhIL-1beta (5 ng/mL) for 3, 6, 9, 12, and 24 hours. Concentration of PGE2 in the media was measured via radioimmunoassay. T...
Lavin TE, Nielsen BD, Zingsheim JN, O'Connor-Robison CI, Link JE, Hill GM, Shelton J.An experiment was conducted to study P digestibility in mature horses because of the growing environmental concerns regarding P runoff and previous equine research focused mostly on young and growing animals or used ponies as a model. Phytase supplementation of swine and poultry diets can result in greater phytate-P digestibility, leading to a decreased need for inorganic P supplementation and a decrease in P excreted to the environment; this, however, has not been demonstrated in the horse. Six mature Arabian geldings were fed 6 diets consisting of pelleted concentrate and alfalfa hay. The co...
Hussein H, Boyaka P, Dulin J, Bertone A.Cathepsin K (CatK) is an important enzyme regulating bone degradation and has been shown to contribute to the immune response. We have studied two inflammatory models in equine bone marrow nucleated cells (BMNCs); the LPS and the unmethylated CpG stimulation with the following objectives to: 1.determine whether CatK inhibition will alter the cytokine secretion by stimulated BMNCs; specifically IL-1β, IL-6, and TNF-α, and 2.determine the changes in BMNCs surface markers' expression and MHC II molecule under CatK inhibition. Cathepsin K inhibition promoted BMNCs viability and reduced cell apop...
Riggs LM, Krunkosky TM, Noschka E, Boozer LA, Moore JN, Robertson TP, Peroni JF.To compare characteristics and enzymatic products of leukocytes detected in the skin and laminar tissues of horses administered black walnut heartwood extract (BWHE) and horses administered purified lipopolysaccharide (LPS). Methods: 25 healthy 5- to 15-year-old horses. Methods: Horses were randomly assigned to receive LPS (20 ng of O55:B5 Escherichia coli endotoxin/kg; n = 5) IV or 6 L of BWHE (10) or water (control group; 10) via nasogastric intubation. Horses were euthanatized 12 hours after treatment or at onset of Obel grade 1 lameness. Laminar tissue samples and skin samples from the mid...
Carraway KL, Colton DG, Shin BC, Triplett RB.Bovine and equine erythrocytes have been studied by three different surface modification techniques to investigate the accessibility of the surface components to the external medium. Lactoperoxidase labeling of equine erythrocytes results in a significant labeling of only one membrane component, a 100 000-mol.wt polypeptide corresponding to the membrane-spanning Component III of human erythrocytes. The major sialoglycoprotein of the equine erythrocyte is not labeled. This is in contradistinction to the situation for human and bovine cells, where both components are labeled. The equine membrane...
Numazawa M, Osawa Y.The metabolic pathway leading to equilin and equilenin biosynthesis in the pregnant mare is different from that of estrone and estradiol and it is apparently cholesterol-independent. The precise precursors and intermediates and the stereomechanism of equine placental aromatization have not been established. [1,2-3H, 4-14C]3-Hydroxy-3,5,7-androstatrien-17-one was synthesized as a potential substrate and the 3H-distribution was analyzed by biochemical and chemical derivatization methods. The substrate was converted to equilin, equilenin and Heard's ketone by horse placental microsomes with a sp....
Chen CH, Albers JJ.The abilities of apolipoprotein A-I species isolated from humans, horses, sheep, goats and rabbits to activate purified human lecithin-cholesterol acyltransferase and the enzyme from homologous plasmas and plasma of other mammalian species were compared. Each purified apolipoprotein A-I species was individually incorporated into phosphatidylcholine/cholesterol vesicles by the cholate dialysis method to form proteoliposome common substrates (apolipoprotein A-I/phosphatidylcholine/cholesterol molar ratio of 1:250:12.5) for the enzyme activity assay. All apolipoprotein A-I species tested had the ...
Tkachenko AG, Winston GW.Preincubation of horse liver alcohol dehydrogenase (HLADH) with the oxidative agent, tert-butyl hydroperoxide (tBOOH) results in a twofold stimulation of the ethanol dehydrogenase activity of this enzyme. This stimulation was dependent on tBOOH concentration up to 100 mM; above this concentration tBOOH did not further stimulate ethanol oxidation by HLADH. Active-site-directed reagents and classical ADH binary complexes were used to probe the possible mechanism of this activating effect. The rate and extent of stimulation by tBOOH is strongly reduced by binary complexes with NAD(+) or NADH, who...
Main AR.The kinetic and structural relationships of eight electrophoretically pure mammalian serum and liver serine carboxylesterases (CE) and cholinesterases (ChE) have been studied. Eight CE's and ChE's, which were fully resolved but only partially purified, provided additional information. Five of the electrophoretically pure esterases were monomeric, and of these, four belonged to a new and widely distributed class. These four monomeric esterases hydrolyzed choline esters, but at widely differing rates. Thus two were termed monomeric butyrylcholinesterases, mBuChE I and II, and two were monomeric ...
Watson ED, Thomson SR.Aromatase P-450 (P-450arom) is a crucial regulatory enzyme that is necessary for conversion of androgens to oestrogens. Corpora lutea and follicles were obtained from the ovaries of cyclic mares and from mares at day 20 and days 40-70 of pregnancy. The presence of P-450arom within specific cell types was investigated by immunostaining to determine potential sites of oestrogen synthesis. Immunoreactivity for P-450arom was confined to the granulosa layer of non-atretic follicles > 5 mm in diameter and to corpora lutea at all stages of the oestrous cycle and during pregnancy. These findings co...
Froscher BG, Nagode LA.The origin of increased alkaline phosphatase (ALP) activity in peritoneal fluid (PF) of horses with clinical signs of abdominal pain was investigated to determine the usefulness of measuring ALP in PF in the diagnosis of small intestinal injury. The ALP isoenzymes in PF from 10 clinically normal horses and from 50 horses with clinical signs of acute abdominal pain were analyzed for their sensitivities to inhibition by L-phenylalanine, L-homoarginine, and levamisole and to inactivation by heat (56 C, 15 minutes). The enzymes also were discriminated by their patterns of migration during polyacry...
Miller SK.1. Results of laboratory experiments which compared horse and human serum butyrylcholinesterase (EC 3.1.1.8) with respect to their acid inactivation and ammonium sulfate protection show: 2. Horse serum butyrylcholinesterase is more resistant to inactivation at pH 3.0 than human serum butyrylcholinesterase. 3. The loss of activity at pH 3.0 for both horse and human butyrylcholinesterase does not follow first order kinetics. 4. Both human and horse serum butyrylcholinesterase are protected from pH 3.0 inactivation by ammonium sulfate concentrations up to 33% saturation (1.37 M).
Riber C, Rubio MD, Marquez F, Pinedo M, Muñoz A, Castejon F.Clinical blood chemistry was studied on 13 Andalusian horses with laminitis. Ten healthy horses were used as controls. Blood samples were taken within the first 24 hr after the onset of the disease in Obel grade 3 before any type of treatment was given. No significant differences were observed in the number of red blood cells and white blood cells between Andalusian horses affected by laminitis and healthy animals. Significant decrease in the number of neutrophils and increased number of lymphocytes were noted. A significant increase in the enzymatic activity of CPK, LDH and AST in these anima...
Moslemi S, Dintinger T, Dehennin L, Silberzahn P, Gaillard JL.The ability of human and equine placental microsomes to aromatize 7 alpha-methyl-19-nortestosterone (MNT) was studied. Kinetic analysis indicates that MNT shares the androgen-binding site of human and equine placental microsomal aromatases. Human placental microsomal estrogen synthetase had about a 2.5-fold higher relative affinity for MNT than the equine placental enzyme (KiMNT/Km androstenedione of 32 versus 87). However, MNT was not metabolized by human placental microsomes, whereas it was very actively metabolized by equine placental microsomes. Further studies using purified equine cytoch...
Nagata S, Kurosawa M, Kuwajima M.A new enzyme immunoassay (EIA) for the measurement of furosemide in horse plasma is described. The lower limit of detection of this EIA method was 7.8 ng/ml. The intra-and inter-assay coefficients of variation ranged from 2.5% to 4.9% and 7.5% to 9.8%, respectively. Cross-reactivity with other compounds was not observed. There was a high correlation (r2=0.987) between the high-performance liquid chromatography and EIA results obtained for furosemide concentrations in horse plasma. These results indicate that the newly developed EIA method is useful for the quantitative analysis of furosemide i...
