Plasma is the liquid component of blood in horses, consisting primarily of water, electrolytes, proteins, and waste products. It serves as a transport medium for nutrients, hormones, and waste products throughout the body. Plasma also plays a role in maintaining blood pressure and volume, as well as serving as a reservoir for critical proteins involved in clotting and immune responses. Research on equine plasma often focuses on its composition, functions, and applications in veterinary medicine, such as transfusions and diagnostic testing. This page compiles peer-reviewed research studies and scholarly articles that explore the properties, functions, and clinical applications of plasma in equine health.
Rose RJ, Kohnke JR, Baggot JD.Plasma phenylbutazone concentrations were determined for up to 12 h in 6 horses following intravenous and oral phenylbutazone administration. To evaluate the bioavailability of different oral preparations, phenylbutazone was administered in a paste as well as the traditional powder form. The effect of the state of stomach contents on the absorption of phenylbutazone was investigated by administering the paste before and after feeding; the powder was given in a small bran mash and a full feed of lucerne chaff, wheaten chaff and bran. Despite great variability among individual horses both the pa...
Snow DH, Munro CD, Nimmo MA.The effects of 7 weekly injections of the anabolic steroid nandrolone phenylpropionate (400 mg) were investigated in 4 healthy, mature geldings. Measurement of body weight, nitrogen retention and plasma urea failed to demonstrate a consistent anabolic effects. Examination of biopsies from the semitendinosus and biceps femoris muscles showed no alteration in water content or glycogen concentration with treatment. Similarly no changes were found in the activities of 6 muscle enzymes. However, a significant increase in the proportion of fast twitch low oxidative fibres of the biceps femoris was o...
Snow DH, Munro CD, Nimmo MA.The effect of 11 weekly injections of nandrolone phenylpropionate (400 mg) was investigated by a crossover trial (2 training periods) in 6 Thoroughbred geldings undergoing training. A decrease in body weight and flank measurement occurred only during the first training period and was not modified by the anabolic steroid. Urinary nitrogen excretion was lower in the anabolic treated animals only in the first training period. Neither training nor training plus nandrolone phenylpropionate administration caused any marked alteration in blood biochemistry or haematology. A significant decrease in pl...
Chapman DI, Close PM, Moss MS, Snow DH.A radioimmunological method was used as a screening procedure to determine the period of detection or "clearance time", for the horse, of therapeutic doses of the synthetic anabolic steroid nandrolone phenylpropionate. Seven horses, either at rest or being exercised, were given a course of weekly intramuscular injections of the steroid. On the separate occasion, some of the horses were given a single intramuscular injection of the same compound. The weekly injections maintained a high plasma concentration of nandrolone and/or metabolites. The mean (+/- sd) period of detection in plasma of thes...
Ralston SL, Baile CA.The hypothesis that changes in blood glucose concentrations and(or) utilization rate affect feeding behavior in ponies was tested. Ponies (n = 4) were fasted for 4 h, then given iv injections of 50% glucose [.2 g glucose/BW.75 kg (low dose, LD) or 1.0 g glucose/BW.75 kg (high dose, HD)] or an equal volume of normal saline (HDS; LDS) 5 min before being allowed access to pelleted feed. Blood samples were drawn at regular intervals pre- and post-treatment and analyzed for plasma glucose (PG), immunoreactive insulin (IRI) and glucagon concentrations. All glucose-treated animals immediately ate mea...
Bottoms GD, Templeton CB, Fessler JF, Johnson MA, Roesel OF, Ewert KM, Adams SB.This study had 2 objectives: (i) to correlate plasma thromboxane and prostaglandin I2 (epoprostenol) concentrations with hemodynamic changes occurring in equine endotoxin shock, and (ii) to determine the effects of flunixin meglumine on plasma concentrations of these prostaglandins relative to hemodynamic changes. Shock was induced in 2 groups, each of 4 anesthetized ponies, and in a 3rd group of 2 ponies. Group A ponies were given endotoxin only (and were not treated), and group B ponies were given endotoxin and then treated with flunixin meglumine. Group C ponies were treated with flunixin m...
Cross AR, Higson FK, Jones OT, Harper AM, Segal AW.1. The absorption coefficient of human neutrophil plasma-membrane reduced-minus-oxidized cytochrome b-245 was determined [delta epsilon (mM; 559-540 nm) = 21.6 cm-1]. 2. Neutrophil polymorphonuclear leucocytes (neutrophils) were prepared from human, ox, horse and pig blood. In each case plasma-membrane fractions were found to contain low-potential cytochrome b. When membranes from horse neutrophils were incubated anaerobically with either NADH or NADPH the cytochrome b became reduced. Prior stimulation of the cells with phorbol myristate acetate did not increase the rate or extent of cytochrom...
Gronwall R, Engelking LR.The effects of several treatments and their routes of administration on the reduction of hyperbilirubinemia in 9 pony mares after a 3-day fast were studied. Treatments were as follows: glucose given at doses of 1.2, 2.4, and 3.7 mg/min/kg of body weight; refeeding the base-line diet; feeding straw; and IV administration of taurocholic acid at a dosage of 0.07 mumol/min/kg. The 3 glucose dosages were each given by 3 different routes: IV, intraduodenal, and intragastric. The smallest dosage of glucose given by IV route reduced the plasma bilirubin concentration only 7%, even though other measure...
Reitnour CM.The influence of administering caecal corn starch (0.0, 0.2, 0.4 or 0.6 g/kg body weight/day) on protein utilisation in 4 ponies was analysed with a latin square experimental design. The basal diet was dehydrated alfalfa pellets. Determinations were made of nitrogen retention, protein and dry matter digestions, total plasma protein, plasma urea nitrogen, plasma ammonia and plasma-free amino acids. Twice daily administration of corn starch into the caecum resulted in an increased nitrogen retention (P less than 0.01). Maximum nitrogen retention was observed with the caecal administration of 0.4...
Zatzman ML, Clarke L, Ray WJ, Garner HE, Traver D.Simultaneous renal clearances of inulin (CIN), p-aminohippurate (CPAH), and creatinine (CCR) were measured in hydrated mares (6 ponies and 2 horses). The CIN and CPAH were determined during steady-state infusion at 3 different infusion rates. A 6-fold change in plasma IN concentration did not produce alteration in CIN, nor was there a difference between the ponies and horses (P greater than 0.2). The overall average (mean +/- SEM) was 190.6 +/- 5.89 ml . min-1 . 100 kg of body weight-1. There was no difference noted between simultaneous CIN and CPAH. Clearance of PAH remained essentially const...
Alexander F.Phenylbutazone administered in therapeutic doses to ponies decreased urinary sodium and chloride excretion. The volume and osmolality of the urine was unaffected as was potassium excretion. Faecal excretion of chloride decreased and that of potassium increased, while faecal sodium excretion was unaffected. Plasma pH, bicarbonate and total carbon dioxide decreased after phenylbutazone administration. Packed cell volume, plasma sodium, potassium, carbon dioxide tension and chloride were unchanged.
Skrabalak DS, Maylin GA.Dexamethasone and a metabolite, 9-fluoro-16α-methyl-6β, 11β, 16β-trihydroxy-1, 4-androstadiene-3, 17-dione, were detected in the urine of horses injected parenterally with the parent drug. The structure of the metabolite was elucidated by thin-layer chromatography, infrared spectroscopy, mass spectroscopy and nuclear magnetic resonance spectroscopy.
Wilson MG, Nicholson WE, Holscher MA, Sherrell BJ, Mount CD, Orth DN.Using RIAs for six regions within proopiolipomelanocortin (proOLMC), gel filtration, and electrophoresis, we studied pituitary peptides in a normal horse and one with Cushing's disease caused by a pars intermedia adenoma. Almost all immunoreactive (IR) ACTH (78%) was 4,500 mol wt (4.5K) ACTH in normal pars distalis, but it was almost 100% corticotropin-like intermediate lobe peptide (CLIP) in normal pars intermedia. alpha MSH and beta MSH were found mainly in pars intermedia: equal concentrations of the beta MSH precursors, beta-lipotropin (beta LPH) and gamma LPH, were found in pars distalis....
Ballard S, Shults T, Kownacki AA, Blake JW, Tobin T.After intravenous (i.v.) injection, acepromazine was distributed widely in the horse (Vd = 6.6 litres/kg) and bound extensively (greater than 99%) plasma proteins. Plasma levels of drug declined with an alpha half-life of 4.2 min, while the beta phase or elimination half-life was 184.8 min. At a dosage level of 0.3 mg/kg acepromazine was detectable in the plasma for 8 h post dosing. The whole blood partitioning of acepromazine was 46% in the plasma phase and 54% in the erythrocyte phase. Penile prolapse was clearly evident at doses from 0.01 mg/kg to 0.4 mg/kg i.v., and the duration and extent...
Rose RJ, Sampson D.Total and individual non-esterified fatty acids (NEFA), pyruvate, lactate, alpha ketoglutarate, acetoacetate, beta hydroxybutyrate, glucose and insulin were measured in horses during an 80 km endurance ride and during four days of food deprivation. In the latter group venous blood-gas and acid-base parameters, and plasma cortisol concentrations were also measured. During exercise and food deprivation the NEFA became considerably elevated, the predominant of which were oleic (35 per cent), palmitic (24 per cent), linoleic (19 per cent) and linolenic (10 per cent). By one hour after feeding tota...
Sklan D, Donoghue S.1. Serum and intracellular distribution of retinol was determined in equines maintained on four levels of vitamin A intake. 2. The form of retinol transported in serum was determined by gel filtration and chromatography to be a complex of retinol bound to a protein of molecular weight (MW) of approximately 20000, which was in turn complexed probably with prealbumin to yield a complex with a MW of 75000 to 80000. 3. Increasing dietary vitamin A levels enhanced the concentration of lipoprotein-bound retinyl esters in the plasma. 4. Vitamin A in the liver cytosol was found predominantly as retiny...
Baker HW, Baker ID, Epstein VM, Hudson B.Cortisol and testosterone were measured by radioimmunoassay in plasma samples from race horses. None of 6 stressed male horses had low cortisol levels but testosterone levels (0.81 +/- 0.15 nmol/l) were significantly lower than in healthy horses (1.86 +/- 0.31 nmol/l). The conclusion was made that adrenocortical insufficiency is not a common association of stress in race horses. The reduction in testosterone levels is probably a nonspecific response similar to that seen in other species.
van Niekerk CH, Morgenthal JC.The depressing effect on plasma progestagen levels of pregnant mares subjected to specific stressful conditions such as severe pain, infectious diseases, emotional disturbances and exogenous corticosteroids are described. It is concluded that the detrimental effect of stress, evident from its negative influence on plasma progestagen concentrations, could play a major role in the occurrence of pregnancy failure in the Thoroughbred mare.
Stewart DR, Stabenfeldt GH, Hughes JP.Plasma relaxin concentrations were measured hourly by radio immunoassay in 4 pregnant mares from 11 days before until 4 days after natural foaling. Pre-partum levels ranged from 4 to 7 ng/ml without any surge until the second stage of labour when they increased rapidly to about 11 ng/ml. In 3 of these mares, relaxin activity declined immediately after the expulsion of the placenta and was below detectable levels within 36 h. In the other mare relaxin activity did not fall until after the mechanical removal of the placenta 7 h after foaling. Eight mares were induced to foal by the administratio...
Turner JW, Kirkpatrick JF.This field study of feral stallions in Montana and Idaho examines and correlates the seasonal pattern of plasma androgens and specific sociosexual behaviour and reports the effect of a long-acting androgenic steroid on this behaviour and on fertility. Plasma testosterone was measured by competitive protein binding assay in samples obtained by jugular venepuncture from captured animals. In samples taken from 34 sexually mature stallions in 6 different months during the year, a definite seasonal pattern in testosterone was present, with a peak in May (3.04 +/- 0.63 ng/ml) and a nadir in December...
Rossdale PD, Silver M, Ellis L, Frauenfelder H.The changes in plasma cortisol concentration in the immediate postnatal period were examined in 3 groups of newborn foals and the response of the adrenal cortex to exogenous ACTH1-24 (tetracosactrin) was tested in 2 of these groups. In full-term Thoroughbred and Pony foals a rise in plasma cortisol occurred between 0 and 30 min after birth, whereas no significant cortisol changes could be detected within 2 h of birth in the group of prematurely delivered foals. These differences in plasma cortisol between term and premature foals were accompanied by differences in blood pH and lymphocyte and n...
Fowden AL, Ellis L, Rossdale PD.Plasma concentrations of insulin and glucose were measured in Pony and Thoroughbred foals at birth and at intervals thereafter for up to 7 days. The plasma concentrations of insulin in foals of both breeds at birth were 11.2 +/- 2.5 microU/ml (N = 6) and 13.5 +/- 1.5 microU/ml (N = 16) respectively. These values were similar to those obtained for foals in utero but were significantly less than those in adult animals. There was little variation in the plasma concentrations of insulin and glucose during the first 2 h of life and both concentrations tended to rise in the next 24-48 h. Although th...
Oltner R, Edqvist LE.Progesterone concentrations in heparinized plasma harvested immediately after blood collection were compared with levels obtained after storage of the corresponding whole blood for 2 h, 4 h, 6 h, 1 day, 2 days and 5 days at room temperature and in a refrigerator. The blood was taken during the luteal phase from 4 dogs, 4 horses, 4 pigs and 8 cows. For 4 cows the storage time was extended to 9 and 20 days. No significant effect of whole blood storage time on plasma progesterone concentrations could be shown for dogs or pigs. For the horse a slight but significant decrease was demonstrated when ...
Fessler JF, Bottoms GD, Roesel OF, Moore AB, Frauenfelder HC, Boon GD.A study was made of flunixin meglumine (FM), an analgesic agent with antiprostaglandin activity, in the management of endotoxin-induced changes in ponies. Three groups of 5 ponies each were used: A--controls, B--nontreated ponies with endotoxin-induced shock, and C--ponies with endotoxin-induced shock treated with FM. Shock was induced in anesthetized ponies with IV injections of Escherichia coli endotoxin. Disruption of glucose homeostasis, insulin levels, hemograms, aerobic metabolism, and cell damage as indicated by plasma enzymes were observed. Treatment with FM (5 minutes) after shock was...
Larson VL, Stowe CM.Oxytetracycline (OTC) was administered IV to 3 clinically normal horses at a dosage of 10 mg of OTC/kg of body weight. Plasma OTC concentrations were determined at 30-minute intervals until postinjection minute (PIM) 240. At PIM 240, the mean OTC concentration in pulmonary tissue was 3.96 microgram/g of tissue (wet weight) and in renal tissue was 25.47 micrograms/g. diluted bronchial fluid had a mean concentration of 0.288 microgram of OTC/ml at PIM 240. The data demonstrated that OTC has adequate tissue distribution in horses.
Greene CE, Tsang VC, Prestwood AK, Meriwether EA.Optimal reaction conditions for the activated partial thromboplastin time (APTT), 1-stage prothrombin time (PT), and Russell's viper venom time were studied for pooled plasmas of horses, cattle, sheep, goats, swine, dogs, cats, and persons. Changes in CaCl2 and NaCl concentrations had significant effects on the APTT and PT reactions. The APTT was more sensitive than the PT to changes in CaCl2 concentration. The CaCl2 concentration recommended by the manufacturer for the APTT was suboptimal for some of plasmas of domesticated animals in ths study. Infusorial earth (Celite, activator) concentrat...
Abass BT, Weaver BM, Staddon GE, Waterman AW.The pharmacokinetics of thiopentone sodium administered intravenously as a single dose (11 mg/kg) were studied in acepromazine pre-medicated horses and ponies in which anaesthesia was maintained with either halothane (Group 1) or isoflurane (Group 2). The results showed that the disposition kinetics of thiopentone in horses and ponies were best described by a three-compartment open model. In plasma, a very short initial distribution phase in both horses and ponies, half-life 1.4 +/- 1.2 min (mean +/- SD) and 1.3 +/- 0.7 min, respectively, was obtained, which was followed by a second comparativ...
Hermann M, Bretscher R, Thiébaud G, Meister D.HAES Steril 10% is a colloidal plasma expander rarely used in veterinary medicine. In this study HAES was used in clinical cases for the treatment of shock and in a comparative hypervolemic hemodilution study (HAES versus lactated Ringer's solution) using two experimental horses. Injection of a HAES volume equivalent to 10% of estimated blood volume resulted in a highly significant drop in PCV and in a significant drop in total protein concentration. Half live of HAES was approximately two hours. No incompatibility reactions were observed. In man HAES improves microcirculation. Studies in prog...
Caltabilota TJ, Milizio JG, Malone S, Kenney JD, McKeever KH.The purpose of this study was to test the hypothesis that sucralfate, a gastric ulcer medication, would alter plasma concentrations of total carbon dioxide (tCO2), lactate (LA), sodium (Na+), potassium (K+), chloride (Cl-) and total protein (TP), as well as calculated plasma strong ion difference (SID) and packed cell volume (PCV) in horses subjected to a simulated race test (SRT). Six unfit Standardbred mares (approximately 520 kg, 9-18 years) were used in a randomized crossover design with the investigators blinded to the treatment given. The horses were assigned to either a control (40-50 m...
Turk MA, Thomas DE.To study the role of cytochrome P-450-dependent mixed function oxidase reactions in equine 3-methylindole (3MI) toxicosis, ponies were given 20 mg of phenobarbital/kg of body weight at 72, 60, 48, 36, and 24 hours before 100 mg of oral 3MI/kg to induce cytochrome P-450 or no treatment (controls). Maximal 3MI plasma concentration was decreased and clearance was faster in phenobarbital-treated ponies. Plasma 3MI was still detectable 12 and 36 hours after dosing in phenobarbital-treated and control ponies, respectively. Phenobarbital treatment induced a distribution phase with transition from a 1...
Martens RJ, Malone PS, Brust DM.Oral lactose tolerance tests were evaluated in 25 healthy foals (principals) assigned to 4 groups of approximately 1 week, 4 weeks, 8 weeks, and 12 weeks of age. Lactose monohydrate (1 g/kg of body weight [in a 20% water solution]) was administered via nasogastric tube after a 4-hour fast. Plasma glucose concentrations were monitored before dosing (0 minutes) and sequentially for 300 minutes. Six control foals were given a volume of water equivalent to the volume of lactose monohydrate administered to principal foals. After oral lactose loading, mean plasma glucose concentrations of all princi...
Díez E, López I, Pérez C, Pineda C, Aguilera-Tejero E.Donkeys appear to be more predisposed than large breed horses to suffer from hyperlipemia. The reason for that predisposition is unknown but anorexia is a consistent feature of the disease. Leptin, a protein synthesized in fat tissue, is one of the major inhibitors of appetite in mammals. Objective: We hypothesized that donkeys could have elevated plasma leptin concentrations compared to horses. Methods: Blood samples were obtained from 50 donkeys for measurement of leptin, triglycerides (TGs), glucose, and insulin. Glucose/insulin ratio, modified insulin to glucose ratio, and reciprocal of th...
Tobin T, Blake JW, Tai CY, Arnett S.Rapid intravenous injection of 1 g of procaine hydrochloride in Thoroughbred mares produced variable signs of central nervous system excitation for as long as 4 minutes. Plasma concentrations of procaine were similarly variable and transient, decreasing with a half-life of approximately 25 minutes. In vitro, plasma from freshly collected equine blood hydrolyzed procaine with a half-life of approximately 7.5 minutes. This hydrolysis was apparently due to plasma esterases. Penicillin, when added free or complexed as procaine-penicillin, did not protect procaine against hydrolysis by these plasma...
Hinchcliff KW, McKeever KH, Muir WW.The systemic haemodynamic and acid-base effects of the administration of phenylbutazone (4.4 mg kg-1 intravenously) to standing and running horses were investigated. Phenylbutazone, or a placebo, was administered to each of six mares either 15 minutes before, or after 30 minutes of a 60-minute submaximal exercise test which elicited heart rates approximately 55 per cent of maximal, and to the same horses at rest. The variables examined included the cardiac output, heart rate, systemic and pulmonary arterial pressures, right atrial and right ventricular pressures, and arterial and mixed venous ...
Butudom P, Foreman JH, Kline KH, Whittem EL.Some methods of lactate (LA) measurement have not been validated appropriately for use in horses. Objective: To validate 2 LA analysers (YSI 2300 Stat Plus and TDx Lactic Acid Assay) for use with equine plasma and to compare plasma [LA] determined by the 2 methods. Methods: Both instruments were evaluated for linearity, parallelism, recovery and precision using serial dilutions of standard LA solutions and equine plasma and then comparing results with linear regression or paired t tests. Plasma [LA] results were compared in 275 blood samples collected from horses exercising at various intensit...
Lanci A, Mariella J, Ellero N, Canisso IF, Dondi F, Castagnetti C.This study aimed to determine alpha-fetoprotein (AFP) concentrations in amniotic fluid, plasma of mares and respective foals: carrying normal pregnancies and delivering healthy foals (n = 20; Group 1); carrying apparently normal pregnancies and delivering sick foals (n = 15; Group 2); carrying high-risk pregnancies and delivering sick foals (n = 14; Group 3). High-risk pregnancy was defined by a history of premature udder development/lactation or increased of the combined thickness of the uterus and placenta, or vulvar discharge and/or mares' systemic illness. Sick foals were affected by...
Tsogtgerel M, Murase H, Moriyama H, Sato F, Nambo Y.Late-term fetal loss in horses is a major problem in the horse-breeding industry globally. Abnormal pregnancies should be diagnosed as early as possible to prevent abortions and other gestational problems. According to our previous longitudinal study in healthy pregnant mares, the plasma activin A concentration increases as pregnancy progresses. The aim of the present study was to compare plasma activin A concentrations in healthy pregnant Thoroughbred mares (n=40) with those in pregnant mares that suffered fetal loss or showed abnormal symptoms (n=30) during late gestation. This field study f...
Garcia P, Perot I, Loup B, Balssa F, Jaubert M, Delcourt V, Dujardin C, Popot MA, Bailly-Chouriberry L.Clodronate is a non-nitrogen-containing bisphosphonate drug approved in equine veterinary medicine. Clodronate is prohibited for use in competition horses; therefore, to set up an appropriate control, detection times and screening limits are required. The quantitative method in plasma consisted of addition of chloromethylene diphosphonic acid as internal standard. Automated sample preparation comprised a solid phase extraction with weak anion exchange properties on microplate. After methylation of the residue with trimethyl orthoacetate, analysis was conducted by high-performance liquid chroma...
Reilly CA, Aust SD.An intracellular, membrane-bound enzyme exhibiting both p-phenylenediamine oxidase activity and ferrous iron oxidase activity was isolated with the plasma membrane fraction of horse heart and studied for its ability to load iron into ferritin. The ferroxidase activity of the tissue oxidase was stimulated approximately twofold by horse spleen apoferritin, and the iron was loaded into ferritin. The loading of iron into ferritin by the tissue oxidase was inhibited by anti-horse serum ceruloplasmin antibody. The stoichiometry of iron oxidation and oxygen consumption during iron loading into ferrit...
Hubbell JA, Hinchcliff KW, Grosenbaugh DA, Beard WL, Beard LA.Frusemide reduces pulmonary vascular pressures in resting horses and attenuates exercise-induced increases in these pressures in exercising horses. The mechanism underlying these effects of frusemide is unclear. We tested the hypothesis that the haemodynamic effects of frusemide are dependent on diuresis by examining the effect of frusemide in anaesthetised horses in which diuresis was prevented by ligation of ureters. Twenty four horses were assigned randomly to one of 4 treatments: 1) frusemide (1 mg/kg bwt i.v.) and intact ureters; 2) frusemide and ligated ureters; 3) saline placebo and lig...
Camargo FC, Robinson NE, Dirikolu L, Berney C, Eberhart S, Derksen FJ, Lehner AF, May J, Hughes C, Tobin T.Trimetoquinol (TMQ) is a very potent and fast acting bronchodilator in horses with heaves. This study assessed the plasma and urinary concentrations of TMQ in horses with heaves following administration via the intravenous (IV, 0.2 microg/kg) and intra-tracheal (IT, 2 microg/kg) routes. TMQ was administered to six horses affected with heaves (RAO - Recurrent Airway Obstruction, used interchangeably) by the above routes and plasma and urine samples collected and stored at -20 degrees C until analyzed. Solid Phase Extraction (SPE) of TMQ was followed by highly sensitive ESI(+)-LC-MS-MS (ElectroS...
Singh AK, Gordon B, Hewetson D, Granley K, Ashraf M, Mishra U, Dombrovskis D.Gas chromatography with chemical ionization mass spectrometry and selected-ion monitoring provided a sensitive method for the screening and confirmation of steroids in horse urine and plasma. Chemical ionization mass spectrometry was more sensitive than the electron impact ionization mass spectrometry for most of the steroids except for testosterone, prednisone-metabolite-2 and prednisolone-metabolite-2. The chromatographic conditions used in this study provided clean separation of different natural and synthetic steroids. Approximately 75-85% of the steroids added to plasma and approximately ...
Baxter GM, Parks AH, Prasse KW.Plasma and peritoneal fluid samples were collected before and after surgery from 6 horses undergoing a ventral midline exploratory laparotomy and from 6 anesthetized control horses. Coagulation/fibrinolytic components measured in the plasma and peritoneal fluid of these horses included the functional activity of antithrombin III, alpha-2 antiplasmin, plasminogen, and protein C, and the concentrations of fibrinogen and fibrin degradation products. Peritoneal fluid antithrombin III, fibrin degradation products, and plasminogen values were significantly increased after surgery (over time) in prin...
Ralston SL, Baile CA.The hypothesis that changes in blood glucose concentrations and(or) utilization rate affect feeding behavior in ponies was tested. Ponies (n = 4) were fasted for 4 h, then given iv injections of 50% glucose [.2 g glucose/BW.75 kg (low dose, LD) or 1.0 g glucose/BW.75 kg (high dose, HD)] or an equal volume of normal saline (HDS; LDS) 5 min before being allowed access to pelleted feed. Blood samples were drawn at regular intervals pre- and post-treatment and analyzed for plasma glucose (PG), immunoreactive insulin (IRI) and glucagon concentrations. All glucose-treated animals immediately ate mea...
Errecalde JO, Landoni MF.The pharmacokinetics of a slow-release theophylline formulation was investigated following intravenous and oral administration at 10 mg/kg in horses. A tricompartmental model was selected to describe the intravenous plasma profile. The elimination half-life (t1/2 beta) was 16.91 +/- 0.93 h, the apparent volume of distribution (Vd) was 1.35 +/- 0.18 L/kg and the body clearance (ClB) was 0.061 +/- 0.009 L kg-1 h. After oral administration the half-life of absorption was 1.24 +/- 0.30 h, and the calculated bioavailability was above 100%. The t1/2 beta after oral administration was 18.51 +/- 1.75 ...
Hohenhaus MU.A rapid progesterone assay for cow's milk was checked as to whether it was applicable to mares' blood plasma. The "Hygia Progesterone-Test" is an on-farm test which serves for qualitative analysis. It is generally unusable for mares' plasma but sufficiently precise only in cases of larger or smaller progesterone levels. In cases of moderate amounts of progesterone the test is imprecise. The test can be carried out quickly and easily, but the preparation of blood samples takes more time than preparation of milk samples. The test can be recommended for usage in veterinary practice only, but not ...
Clarke LL, Garner HE, Hatfield D.Acute laminitis-hypertension was produced by carbohydrate overloading of the gastrointestinal tract in 12 adult horses. Obel grade 3 (OG3) lameness developed 40 hours (+/- 3.5, SEM) after overfeeding. At OG3 lameness, mean plasma volume was significantly decreased (P less than 0.005) when compared with base-line values. Before OG3 lameness, transient decreases in serum phosphorus and calcium were recorded. Mild hyponatremia also developed before OG3 lameness and persisted. After establishment of OG3 lameness, persistent hypokalemia and increased plasma aldosterone concentration occurred coinci...
Brück I, Lehn-Jensen H, Yde G.A Warmblood mare was observed to ovulate spontaneously 12 follicles within 2 days, none of which exceeded 22 mm in diameter. On Days 13 and 17 after ovulation, 6 embryonic vesicles were identified in the uterus by ultrasonography but by Day 26, 5 of the vesicles had disappeared. Development of the surviving conceptus was monitored until Day 42. Plasma progesterone concentrations rose to 14 ng/ml on Day 7, decreased over the next 8 days and then plateaued to around 4-6 ng/ml until Day 70. The occurrence of multiple spontaneous ovulations was diagnosed repeatedly in this mare. However, the devel...
Knight PK, Ray SP, Rose RJ.Because the haemoglobin concentration Hb[ during exercise may be at the upper limit of blood viscosity for effective oxygen delivery, we hypothesised that administration of blood would not further enhance oxygen delivery or exercise capacity. Six Thoroughbred geldings were used in 5 incremental treadmill exercise tests over a period of 4 weeks. The first test was performed 6 days prior to phlebotomy, which involved the removal of 20 ml/kg bwt of venous blood. Exercise tests were performed at 1, 8 and 15 days after blood removal. Six days after the 15 day post phlebotomy exercise test, blood fr...
Allen AL, Myers SL, Searcy GP, Fretz PB.The Hematologic values of 19 equine fetuses between 202 and 238 days gestation were compared with those of their dams. The red blood cell (RBC) count, hemoglobin concentration, hematocrit, and mean corpuscular hemoglobin concentration were significantly lower in fetal blood, while the mean corpuscular volume, mean corpuscular hemoglobin, and red cell distribution width were significantly higher. Mares had a significantly higher nucleated blood cell count than fetuses, and all nucleated cells were leukocytes (WBC). Most WBC in mare blood were segmented neutrophils and lymphocytes. In contrast, ...
Fielding CL, Magdesian KG.To evaluate changes in electrolyte concentrations and hydration status that take place in endurance horses prior to the start of a competition and determine whether these changes would be associated with elimination. Methods: 19 horses entered in the 2016 Tevis Cup 100-Miles (160 km) One-Day Western States Trail Ride. Methods: Heparinized blood samples were collected at 5 time points: prior to transport to the ride (T0), during check-in the day before the ride (T1), 1 to 2 hours before the start of the ride (T2), at the 15-km mark (T3), and at the 55-km mark (T4). Packed cell volume and plasma...
Wong DM, Vo DT, Alcott CJ, Peterson AD, Brockus CW, Hsu WH.Arginine vasopressin (AVP) has received increased attention in equine critical care but there is minimal information of AVP concentration in foals. The clinical usefulness of measuring AVP in ill foals depends on knowledge of age-related changes in AVP concentrations in healthy foals. Objective: Plasma AVP concentrations will be significantly different when measured from birth to 3 months of age in healthy foals. Methods: Thirteen healthy university-owned foals. Methods: Prospective, observational study. Blood was collected from healthy foals at birth and 3, 5, 7, 10, 14, 21, 28, 42, 56, and 8...
Rauws AG, van Schothorst M, Frik JF.The protein binding, the plasma half-life and the residue depletion of sulfamonomethoxine (SMM) after intramuscular administration were investigated in pigs, horses and cattle. Protein binding was weakly concentration-dependent. The bound fraction in plasma in the therapeutic range amounted to approximately 45, 40 and 50% for pigs, horses and cattle respectively, and the plasma half-lives were approximately 5.1, 5.7 and 3.1 hours respectively. SMM levels were less than 1 mug/g in muscle tissue after 36, 20 and 12 hours in pigs, horses and cattle respectively. In the kidney SMM levels were not ...
Lipscomb DL, Boudreaux MK, Paxton R, Spano J, Welles EG, Schumacher J.To establish the existence of platelet-derived proteins in equine plasma, with the future goal of developing an assay for the detection of in vivo platelet activation. Methods: 5 mature healthy horses. Methods: Platelet-rich plasma and platelet-poor plasma were prepared from anticoagulated blood. Platelets were separated from plasma proteins by gel filtration, then activated with 0.5 microM platelet-activating factor. Protease inhibitors were added, and the released platelet proteins were harvested. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was performed on the released platele...
Knox DA, Ravis WR, Pedersoli WM, Spano JS, Nostrandt AC, Krista LM, Schumacher J.Six healthy mature horses were orally administered a single dose of phenobarbital (26 mg/kg of body weight), then multiple doses (13 mg/kg) orally for 42 consecutive days. Seventeen venous blood samples were collected from each horse after the single dose study and again after the last dose on day 42. Plasma phenobarbital concentration was determined by use of a fluorescence assay validated for horses. Additional blood samples (n = 11) were collected on days 8 and 25 to determine peak and trough concentrations, as well as total body clearance. Phenobarbital disposition followed a one-compartme...
Schott HC, Bohart GV, Eberhart SW.Efflux of potassium (K+) and lactate (lac-) from active skeletal muscle during high intensity exercise leads to increased plasma [K+] and [lac-] in venous and arterial blood. The exercise-induced increases in these ions in human athletes is ameliorated, in part, by uptake by noncontracting tissue, reflected by an increase in the arteriovenous difference across these tissues from rest to exercise. To test the hypothesis that these ions are taken up by noncontracting tissue in strenuously exercising horses, plasma [K+] and [lac-] were measured in blood samples collected simultaneously from the c...
