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Topic:Biochemistry
The study of biochemistry in horses encompasses the chemical processes and substances that occur within equine organisms. This field investigates the molecular interactions and pathways that are fundamental to horse physiology, including metabolism, enzyme activity, and genetic expression. Key areas of interest include the examination of metabolic disorders, nutrient absorption, and the biochemical basis of muscle function and energy production. Researchers utilize biochemical analysis to understand health and disease mechanisms in horses, contributing to the development of diagnostic tools and therapeutic strategies. This page gathers peer-reviewed studies and scholarly articles that explore various biochemical processes and their implications for equine health and performance.
Structure of the alpha 1 subunit of horse Na,K-ATPase gene. Genomic DNA for Na,K-ATPase alpha 1 subunit was obtained from libraries of horse kidney genomic DNA in Charon 4A and in EMBL3 bacteriophages by screening with the full sized cDNA probe of the alpha 1 subunit of rat Na,K-ATPase as probe. The gene spans 30 kb and consists of 23 exons and 22 intervening sequences. Intron-exon boundaries were analyzed. The protein-coding nucleotide sequence encodes 1016 amino acids with an Mr of 112,264. The putative amino acid sequence of horse alpha 1 is 96-97% homologous to those of other mammalian species.
Equine peritoneal macrophage production of thromboxane and prostacyclin in response to platelet activating factor and its receptor antagonist SRI 63-441. The formation of eicosanoids may be a primary route through which platelet activating factor (PAF) exerts its effects during endotoxemia. Since endotoxemia is a common cause of death in horses, a study was conducted to determine whether PAF could stimulate equine macrophage release of thromboxane A2 (TxA2) and prostacyclin (PGI2) and whether a PAF-receptor antagonist would alter macrophage eicosanoid synthesis. Equine peritoneal macrophages were cultured from clinically normal horses and exposed to various concentrations of PAF, the PAF-receptor antagonist SRI 63-441, endotoxin, or a combinati...
In-vitro plasma protein binding of propafenone and protein profile in eight mammalian species. The protein binding of propafenone in vitro was assessed in plasma of mouse, rat, rabbit, dog, sheep, man, cow, and horse at two concentration levels. In all species and at both concentrations propafenone was found highly bound (86-99%) to plasma proteins. No significant relationship was found between free propafenone and the plasma protein fractions. A concentration-dependency was seen in plasma of mouse, sheep, man, and horse, in which the free fraction of propafenone became larger on raising the concentration. Qualitative and quantitative differences were observed in the protein plasma prof...
Serum angiotensin converting enzyme activity and response to angiotensin I in horses. The activity of serum angiotensin converting enzyme (ACE) for healthy horses was 64 +/- 13 mUnits/ml. In vitro, equine serum ACE was sensitive to the following inhibitors (IC50): enalapril (570 nM or 215 ng/ml), captopril (190 nM or 41.3 ng/ml), and enalaprilat (6 nM or 2.1 ng/ml). The intravenous (i.v.) administration of angiotensin I to six healthy horses produced a dose proportional pressor response. The maximal increase in mean arterial pressure over baseline values was 65.6 mmHg at angiotensin I doses of 500 ng/kg bodyweight (bwt). The attenuation of this response to angiotensin I was fur...
The sequence-specific assignment of the 1H-NMR spectrum of an enzyme, horse-muscle acylphosphatase. A complete range of two-dimensional NMR experiments was used for the assignment of the 1H-NMR spectrum of horse muscle acylphosphatase. Firstly the spin systems of some easily identifiable amino acid side chains were assigned. These side chains involved all the aromatic residues and all the leucine, valine, isoleucine, threonine, alanine, proline as well as some of the glycine residues. Analysis of nuclear Overhauser enhancement spectra in our previous work had identified the sequential and long-range patterns characteristics for secondary structure elements. This result had also provided the ...
Relationship of cadmium accumulation to zinc or copper concentration in horse liver and kidney. The concentrations of Cd, Zn, Cu, and metallothionein (MT) in the liver, renal cortex, and renal medulla were determined in 24 male and 15 female younger thoroughbreds (age 27 to 97 months) and two old male horses (age 154 months and 190 months). High correlations were found between Zn and MT in the liver (partial correlation coefficient 0.836), between Cd and MT in the renal cortex (partial correlation coefficient 0.786), and between Cd and Zn in the renal cortex (partial correlation coefficient 0.675), while the correlation between Cd and MT in the liver was low (partial correlation coeffici...
Renal effects of dopamine infusion in conscious horses. An ultrasonic flow probe was implanted around a branch of the left renal artery in five horses. The effects of dopamine were studied in the unsedated horses 10 days after surgery. Three experiments, separated by at least two days, were performed in random order on each horse. In two experiments, dopamine was infused intravenously for 60 mins at either 2.5 and 5.0 micrograms/kg bodyweight (bwt)/min. Saline was infused for 60 mins before and after each infusion, and for 180 mins in the third experiment as a control. Renal blood flow increased during administration of dopamine at both dose rates ...
Effect of an osmotic stimulus on the secretion of arginine vasopressin and adrenocorticotropin in the horse. Arginine vasopressin (AVP) is released in response to changes in blood osmolality and is also a putative secretagogue for ACTH. However, it is unclear whether osmotically generated increases in AVP in the physiological range influence ACTH secretion. We have studied this question using our unique noninvasive technique for collecting pituitary venous blood in six normal conscious horses that received an iv infusion of hypertonic saline (HS; 5%, 0.07 ml/kg.min) for 45-60 min. Pituitary and jugular venous samples were collected every 5 min for 40 min before, during, and for 20 min after HS. Durin...
Effects of diet and feeding on postprandial serum gastrin and insulin concentration in adult horses. Gastrin is the only hormone known to stimulate secretion of hydrochloric acid. It also has trophic effects on specific parts of the mucosa of the gastrointestinal tract. Using radioimmunoassay techniques, postprandial serum gastrin and insulin concentrations were measured in six adult horses to establish effects of different diets on gastrin concentrations. Insulin concentrations were measured to provide support to the patterns of gastrin secretion because patterns of insulin secretion were already known. The horses were fed coastal bermuda hay, or twice daily 5 kg of a complete pelleted ratio...
Identification and description of beta-structure in horse muscle acylphosphatase by nuclear magnetic resonance spectroscopy. Nuclear magnetic resonance spectra of acylphosphatase were searched for signs of beta-structure, i.e. characteristic nuclear Overhauser enhancement patterns displayed in the two-dimensional spectra, typical chemical shifts, coupling constants and slow 2H-H exchange. The results provided identification of the main-chain resonances of amino acid residues involved in the beta-structure. The full sequential assignment of this region was gained by identification of some amino acid spin systems and their alignment with the primary sequence. The assignment of the side-chains was virtually completed s...
Androgen synthesis and aromatization by equine corpus luteum microsomes. Whereas mare corpus luteum does not produce androgens or estrogens in vivo, the incubation of mare corpus luteum microsomes with progesterone and NADPH resulted in 17 alpha-hydroxyprogesterone and estrogen production with a small yield of androstenedione. In the presence of an aromatase inhibitor (4-hydroxyandrostenedione), 17 alpha-hydroxyprogesterone and androstenedione were accumulated. Aromatization of testosterone and androstenedione occurred via stereospecific loss of the 1 beta, 2 beta hydrogen atoms and was inhibited by MgCl2, KCl, and EDTA. The Km of estrogen synthetase from equine co...
Variations in serum sorbitol dehydrogenase, aspartate transaminase, and isoenzyme 5 of lactate dehydrogenase activities in horses given carbon tetrachloride. Seven horses were given 0.5 mg of carbon tetrachloride/kg of body weight via a nasogastric tube. Subsequent hepatocellular damage was monitored by serum enzyme determinations of sorbitol dehydrogenase, isoenzyme 5 of lactate dehydrogenase, and aspartate transaminase activities. Creatinine kinase activity was evaluated as an indicator of muscle cell damage. Sorbitol dehydrogenase, isoenzyme 5 of lactate dehydrogenase, and aspartate transaminase activities were significantly (P less than 0.05) increased by 24 hours after carbon tetrachloride administration. Isoenzyme 5 of lactate dehydrogenase a...
Equine body temperature and progesterone fluctuations during estrus and near parturition. Body temperature and serum progesterone concentrations were measured in mares to determine if a change in either could be useful in predicting estrus, ovulation or parturition. There was no significant correlation (P > 0.1) between rectal temperature and the environmental temperature or progesterone concentration. Progesterone concentration did correlate with stage of estrous cycle and the stage of pregnancy. Significant differences (P < 0.05) in temperature were noted at different times throughout the day. No change in temperature occurred that could be utilized to predict estrus, ovula...
Effects of phenylbutazone on glucose tolerance and on secretion of insulin in healthy geldings. The effect of phenylbutazone (4.4 mg/kg of body weight, IV, q 24 h, for 5 days) on glucose tolerance and on secretion of insulin in 6 healthy geldings was determined. Phenylbutazone significantly lowered fasting concentrations of glucose in plasma but did not significantly change the concentration of insulin in serum. There was no significant effect of phenylbutazone on glucose tolerance, on secretion of insulin, or on the area under the insulin/glucose ratio vs time curve in healthy geldings, as determined by paired t test analysis.
Observations on gamma-glutamyl transferase, 5′-nucleotidase and leucine aminopeptidase activities in the plasma of the horse. In 18 horses there was no effect of age or sex on plasma activities of gamma-glutamyl transferase (gamma-GT), 5'-nucleotidase (5'-NT) and leucine aminopeptidase (LAP). All the enzymes were equally stable after storage for one month at -20 degrees C and there was no significant difference between their activities in serum and plasma in clinically normal horses. The pattern of release of gamma-GT, 5'-NT and LAP into plasma was studied in 114 horses which had a variety of orthopaedic, gastrointestinal, cardiovascular and hepatic (necrosis, lipidosis, neoplasia and cirrhosis) conditions. A definit...
(+)-[3H]-PN 200-110 binding to cell membranes and intact strips of portal vein smooth muscle: characterization and modulation by membrane potential and divalent cations. 1. Specific binding of the calcium-antagonist dihydropyridine derivative, (+)-[3H]-PN 200-110 (isradipine), to cell membranes of equine portal vein smooth muscle was compared with binding to intact strips isolated from rat portal veins. 2. Specific binding to vascular smooth muscle membranes was of high affinity, saturable and reversible. The dissociation constant obtained from association and dissociation kinetics of (+)-[3H]-PN 200-110 was similar to that obtained from equilibrium binding and competition experiments. 3. Specific binding of (+)-[3H]-PN 200-110 was completely displaced by unla...
Identification of the gB homologues of equine herpesvirus types 1 and 4 as disulphide-linked heterodimers and their characterization using monoclonal antibodies. Equine herpesvirus types 1 and 4 (EHV-1 and EHV-4) labelled with [14C]glucosamine were purified from infected cell culture medium and profiles of their structural proteins were obtained that enabled identification of the major glycoproteins. Nine glycosylated polypeptides were identified for each virus. Preparations of the purified viruses each contained a glycoprotein which was linked by disulphide bonds, as determined by diagonal gel electrophoresis under reducing/non-reducing conditions. High Mr forms of this glycoprotein were detected for EHV-1 when the sample was not heated. The EHV-1 pro...
[The occurrence and significance of plasma coagulase negative staphylococci from the genital tract of horses]. Classification based on biochemical characteristics of 389 strains of plasma-coagulase-negative (plc-) staphylococci isolated from the genital tract of mares and stallions resulted in the following distribution of species: St. sciuri 130 (33.4%), St. equorum 42 (10.8%), St. xylosus 16 (4.1%), St. epidermidis 35 (9.0%), St. simulans 24 (6.2%), St. haemolyticus 33 (8.5%), St. warneri 18 (4.6%), St. lentus 12 (3.1%), St. hyicus 11 (2.8%). Strains of St. cohnii, St. capitis, St. gallinarum, St. saprophyticus and St. hominis have only been found sporadically (a. 1%). 48 (12.3%) strains could not be...
The preparation and biochemical characterization of intact capsids of equine infectious anemia virus. Capsids of equine infectious anemia virus have been isolated as cone-shaped particles 60 x 120 nm in size. Detergent treatment of whole virus followed by two cycles of rate-zonal centrifugation in Ficoll produces these capsids in a yield of approximately 10%. The major protein components are the gag-encoded p11 nucleocapsid protein and p26 capsid protein, which are present in equimolar amounts. Substantial cleavage of p11 to p6 and p4 can be observed under conditions where the viral protease packaged in the capsid is enzymatically active.
Differences between individuals in high-molecular weight glycoproteins from mammary epithelia of several species. Milk fat globules are secreted by envelopment in plasma membrane of the lactating cell. SDS-gel electrophoresis of proteins from this membrane has revealed differences between milk donors in two mucin-like glycoproteins. One of these glycoproteins resolves in 3% acrylamide stacking gel and the other in 4% running gel. The proteins vary in number of bands (one or two) and band mobilities. This polymorphism arises, at least in part, from expression of hypervariable genes. In this study, gel electrophoretic evidence of similar polymorphism in glycoproteins from cow, chimpanzee, horse and human mi...
Metabolism and pharmacokinetic studies of propionylpromazine in horses. The propionylpromazine concentrations in plasma after intramuscular administration to horses were determined using gas chromatography with nitrogen-phosphorus detection. After hydrolysis by beta-glucuronidase/arylsulphatase, the parent drug and three metabolites were detected in urine. The metabolites were identified as 2-(1-hydroxypropyl)promazine, 2-(1-propenyl)promazine and 7-hydroxypropionylpromazine by gas chromatography-mass spectrometry. No N-demethylated or sulphoxidated metabolites of propionylpromazine were observed in the horse urine.
Nonequivalence of the two subunits of horse erythrocyte glutathione transferase in their reaction with sulfhydryl reagents. Glutathione transferase (EC 2.5.1.18) from horse erythrocytes has been purified and some molecular and kinetic properties have been investigated. It appears to be a dimeric protein composed of subunits of about 23 kDa, indistinguishable either in sodium dodecyl sulfate or in urea electrophoresis. Amino acid composition, substrate specificities, sensitivity to inhibitors, CD spectra, and immunological studies provide evidence that the horse enzyme is related to the pi class transferases. This enzyme has only two reactive thiol groups/dimer whose integrity appears to be essential for the activit...
Urinary excretion of pentoxifylline and its metabolites by standardbred mares. The urinary excretion of a sustained-release formulation of pentoxifylline was studied in the horse after the oral administration of 4.0 grams of Trental tablets. Urine samples were collected for 24 hours after dosing and analyzed for pentoxifylline and its metabolites using high-performance liquid chromatography coupled with an ultraviolet detector. Six metabolites of pentoxifylline were identified in horse urine in addition to less than 0.2% of unchanged drug. Concomitant use of gas chromatography/mass spectrometry allowed for the elucidation of the chemical structures of the metabolites. Me...
Semen selenium content and sperm mitochondrial volume in human and some animal species. Selenium (Se) and glutathione peroxidase (GSH-Px) were determined from the seminal plasma samples and spermatozoa of human and four different animal species. The human sperm Se concentration was 1.8 +/- 0.8 micrograms/g dry weight, which was about half of that in the bull. Abnormal sperm morphology and motility correlated with low sperm Se content. The volume of sperm mitochondrial sheath in human, bull and stallion was measured using transmission electron microscopy. In these species the sperm Se content was highly correlated with the volume of mitochondria. Among the five species studied, th...
Basal and bile salt-stimulated bile flow and biliary lipid excretion in ponies. The role of bile salt in biliary lipid excretion was studied in 3 healthy ponies with chronic external biliary fistulas. After endogenous bile salt pool depletion, micelle-forming taurocholate or taurochenodeoxycholate was infused to replace excreted bile salt. Enterohepatic circulations were held open (total biliary diversion) throughout each study. Results indicated that biliary lipid excretion in ponies (113 +/- 21 nmol/min/kg of body weight) is approximately 10 times less than that reported in rodents. Although the lipid composition (4.4% cholesterol, 5.6% phospholipid, and 90% bile salt) ...
Synthesis and aromatization of 19-norandrogens in the stallion testis. The results of the measurement of 19-nortestosterone in the testiscular artery and vein of the stallion, the very low levels of this steroid in the peripheral blood of geldings and the similar patterns of increase in the peripheral levels of 19-nortestosterone and testosterone after hCG stimulation, show that 19-nortestosterone, like testosterone, is essentially synthesized in the testis. This testicular origin was confirmed by the ability of testicular tissue to synthesize 19-norandrogens from [4-14C]androgens in vitro. 19-Nortestosterone was 50% conjugated in the peripheral blood and almost ...
Pharmacologic effects and detection methods of methylated analogs of fentanyl in horses. Pharmacologic effects of alpha-methylfentanyl and 3-methylfentanyl, analogs of fentanyl, were investigated in mares. The ability of an 125I-labeled fentanyl radioimmunoassay (125I-RIA) to detect these methylated fentanyl analogs in individual and pooled urine samples from horses was evaluated. Also, the ability of 7 fentanyl antibodies to react with fentanyl and fentanyl derivatives (sufentanil, alfentanil, and carfentanil) was investigated. Mares were studied in a locomotor test to determine the amount of stimulation methylated fentanyl analogs might induce. Two mares each were given alpha-me...
