Distribution of 5'-nucleotidase in the tissues of sheep and the effect of kidney and liver lesions on the activity of the enzyme in plasma and urine

The distribution of 5'-nucleotidase (5'-NT) activity in the tissues of the sheep differs from that of gamma glutamyl transferase (GGT). Nevertheless, both enzymes are released into the plasma of sheep which have been infected with Fasciola hepatica or in which the bile duct has been ligated. In a sheep dosed with sporidesmin, a fungal toxin which damages the biliary tract, there was an increase in GGT activity in the plasma and urine but no change in 5'-NT activity. Neither enzyme was released into the plasma or urine of sheep dosed with carbon tetrachloride. In sheep with renal tubular necrosis and hepatocellular necrosis caused by dosage with hexachlorobutadiene, both enzymes were released into the plasma, and GGT, but not 5'-NT activity was found in urine. In sheep with tubular necrosis of the kidney caused by the administration of mercuric chloride, GGT activity, but not 5'-NT, increased in the plasma and urine.     

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 definitive diagnosis of hepatic disease was established by histological examination of the liver. gamma-GT and 5'-NT were leaked into plasma in hepatic disease and gamma-GT was the more sensitive indicator of liver damage. There was some evidence that gamma-GT and 5'-NT plasma activities may increase in hepatic necrosis as well as in biliary obstruction. LAP was insensitive and not hepatic specific in the horse.     

Distribution of 5'-nucleotidase and gamma glutamyl transferase activities in the tissues of the horse

In the horse, 5'-nucleotidase (5'-NT) activity is found mainly in homogenates of lung, kidney, small intestine, mammary gland, liver and pancreas. Lower activities are present in brain and muscle. Activity can be demonstrated histochemically in the glomeruli and tubules of the kidney, in the sinusoidal borders of the hepatocytes and the bile duct epithelium as well as in the blood vessels of all organs. There is no significant difference between the 5'-NT activity in serum and plasma of normal horses and of horses suffering from a range of orthopaedic conditions. Previous findings that gamma glutamyl transferase activity is greatest in kidney and high in liver and pancreas have been confirmed.     

Chronic subclinical ovine fascioliasis: plasma glutamate dehydrogenase, gamma-glutamyl transpeptidase and aspartate aminotransferase activities and their significance as diagnostic aids

The effect of low grade chronic Fasciola hepatica infection on the concentration of plasma glutamate dehydrogenase (GD), gamma-glutamyl transpeptidase (gamma-GT) and aspartate aminotransferase (AST) was investigated in sheep dosed daily with three (AL3), eight (AL8) or 14 (AL14) metacercariae over 22 weeks or given a single dose of 200 metacercariae. Significant increases in plasma GD activity first occurred after nine, 12 and 23 weeks and in gamma-GT activity after 12, 24 and 32 weeks for groups AL14, AL8 and AL3 respectively. Changes in AST activity were not as clearly related to dose level. In sheep with single infection, both GD and gamma-GT were capable of detecting liver damage resulting from the migration of 10 or more flukes. Plasma GD and gamma-GT activities are more sensitive indicators of liver cell damage in chronic subclinical fascioliasis than AST activity and gamma-GT may be more suitable as a diagnostic aid on account of its greater stability.     

The pharmacokinetics of xylazine hydrochloride: an interspecific study

The pharmacokinetic disposition of xylazine hydrochloride is described after both intravenous and intramuscular injection of a single dose, in four domestic species: horse, cattle, sheep and dog, by an original high performance liquid chromatographic technique. Remarkably small interspecific differences are reported. After intravenous administration, systemic half-life ( t _{1/2 β}) ranged between 22 min (sheep) and 50 min (horse) while the distribution phase is transient with half-life ( t _{1/2 α}) ranging from 1.2 min (cattle) to 5.9 min (horse). The peak level of drug concentration in the plasma is reached after 12–14 min in all the species studied following intramuscular administration. Xylazine bioavailability, as measured by the ratios of the areas under the intravenous and intramuscular plasma concentration versus time curves, ranged from 52% to 90% in dog, 17% to 73% in sheep and 40% to 48% in horse. The low dosage in cattle did not permit calculation. Kinetic data are correlated with clinical data and the origins of interspecific differences are discussed.     

Antipyrine, erythromycin and oxytetracycline disposition in experimental fasciolosis.

The effects of fasciolosis on drug disposition were studied by administration of antipyrine, erythromycin and oxytetracycline to sheep and cattle. Fasciolosis was produced by administration of 200 or 400 metacercariae (MC) of Fasciola hepatica to sheep and 500 MC to cattle. The disease was subsequently confirmed by determination of plasma glutamate dehydrogenase and gamma-glutamyl transferase and identification and quantitation of mature flukes in the liver at necropsy. Acute or subacute fasciolosis in sheep was accompanied by a significant decrease in the elimination rate constant (beta) and increase in the elimination half-time (t 1/2) for antipyrine and erythromycin when compared with controls or infected sheep which had been treated with the anthelmintic luxabendazole. An increase in apparent volume of distribution (Vd) was seen only for erythromycin in sheep given 400 MC. There were no changes in the disposition of oxytetracycline in sheep with either acute or subacute infection and no effects on disposition of the three test drugs in chronically infected sheep. With early chronic disease in calves, only the disposition of oxytetracycline was affected; not that of antipyrine or erythromycin.     

Presence of salicylic acid in standardbred horse urine and plasma after various feed and drug administrations

Plasma and urinary levels of salicylic acid were examined in Standardbred mares after administration of various feeds, containing different compositions of hay. In addition, horses were administered acetylsalicylic acid orally and methyl salicylate topically. Elevated salicylic acid levels were observed in horse urine and plasma in animals fed lucerne hay. The plasma and urinary elimination of salicylic acid exhibited a diurnal pattern which was related to the type of feed and the feeding schedule. Within 24 h after oral administration of acetylsalicylic acid, plasma and urine salicylic acid levels were consistent with residual levels observed after feeding lucerne hay. Elimination of salicylic acid was rapid and complete, with a half-life between 5 and 7 h. Topical administration of methyl salicylate (8.4 g) produced elevated urinary salicylic acid levels for 6 h. A smaller dose of methyl salicylate (3.4 g) did not elevate plasma or urine salicylic acid levels above those observed following administration of lucerne hay.     

Disposition kinetics of enrofloxacin (Baytril 5%) in sheep and goats following intravenous and intramuscular injection using a microbiological assay

The pharmacokinetics of enrofloxacin were determined in Desert sheep and Nubian goats after intravenous and intramuscular administration of Baytril at the dose of 5mgkg(-1) bodyweight. A two compartment open model best represented the intravenous plasma concentration versus time data in both species. Comparisons between the means of the pharmacokinetic parameters obtained after intravenous administration of enrofloxacin (Baytril) revealed a significantly smaller distribution rate constant (lambda(1)) and consequently a shorter half-life time of distribution in sheep (P<0.05). A larger volume of the central compartment (Vc) was observed in goats (P<0.05). Similar values were obtained for sheep and goats for the remaining parameters.Plasma concentrations versus time data of enrofloxacin after 5mgkg(-1) intramuscular administration of Baytril in sheep and goats were adequately described by one-compartment open model with first order absorption and elimination. There were no significant differences between sheep and goats in any of the estimated pharmacokinetic parameters.The results indicate that the pharmacokinetics of enrofloxacin did not differ significantly between sheep and goats; similar intravenous and intramuscular dose rates of enrofloxacin should therefore be applicable to both species. Owing to the high variations in MIC (minimal inhibitory concentration) of sensitive veterinary pathogens, it is recommended that enrofloxacin dosage regimens be calculated according to the sensitivity of the individual pathogen, site of infection and clinical response, than by following a preset dosage regimen.     

The disposition of suxibuzone in the horse

A high performance liquid chromatographic method is described to determine the anti-inflammatory drug suxibuzone (SXB) and its major metabolites phenylbutazone (PBZ) and oxyphenbutazone (OPBZ) in equine plasma and urine. When suxibuzone (6 mg/kg) was administered intravenously (i.v.) or orally (p.o.) no parent drug was detected in plasma or in urine. The disposition of the metabolite PBZ (i.v.) could be described by a 2 compartment model with a P half-life varying from 7.40 to 8.35 h. Due to severe side effects the use of i.v. suxibuzone should not be encouraged in the horse. PBZ and OPBZ were detected in plasma and urine after p.o. SXB administration. Peak plasma PBZ concentrations (8.8 ± 3.0 μg/ml) occurred 6 h after oral dosing and the terminal exponential constant was 0.11 ± 0.01 h^-1. Phenylbutazone and oxyphenbutazone were detectable in urine (> 1 μg/ml) for at least 36 h, after p.o. administration.
SXB was not hydrolyzed in vitro by horse plasma. Equine liver homogenates however appeared to have a very high capacity for hydrolysing SXB, indicating that first-pass effect could be responsible for the rapid disappearance of this NSAID in the horse.     

gamma-Glutamyl transpeptidase activity in sheep serum: normal values and an evaluation of its potential for detecting liver involvement in experimental lupinosis.

A brief survey of the literature on gamma-glutamyl transpeptidase (gamma-GT) activity is included in this study. The levels of activity in the serum of normal Merino sheep (13,6-32,4 mI.U/ml) were ascertained as a preliminary to following the activity through the entire course of experimentally induced ovine lupinosis, a hepatotoxicosis caused by Phomopsis leptostromiformis (Kühn) Bubák. The response of the serum level of gamma-GT activity to the course of the disease was compared with that of glutamate oxaloacetic transaminase (GOT) and 2 liver function tests for the purpose of assessing its potential application in the study of this mycotoxicosis. Because the levels of activity of gamma-GT were more valuable for the early diagnosis of low grade acute intoxication and the detection of chronic liver involvement while those of GOT gave better information on the development of severe acute hepato-cellular damage, these 2 enzymes, considered together, were found to give the best information on the course of the toxicosis. The changes in gamma-GT activity during various stages of intoxication were also related to the histopathological lesions in the liver.     

ELISA detection of fentanyl in horse urine and plasma

The prototype of a commercial ELISA test kit designed for fentanyl determination in human urine has been evaluated for screening fentanyl in horse urine and plasma. The measurement of fentanyl after intravenous (2 mg) and intramuscular (0.25 mg) administration in undiluted plasma was not reproducible while accurate quantification of fentanyl in urine greatly depends on the composition of the horse urine. The ELISA assay, however, is simple and could be successfully used for quantitative measurements in diluted urine and for rapid qualitative screening for fentanyl in large numbers of urine samples.     

Electroanaesthesia or electroimmobilisation of calves, sheep and pigs by the Feenix Stockstill

Since the end of the last century many investigations with electroanaesthesia have been performed in animals and man. The interest in this method of anaesthesia has emerged because anaesthesia is achieved immediately after the onset of the current and the recovery is very rapid after cutting off of the current. Recently a battery operated apparatus became available (Feenix Stockstill) for application of electroanaesthesia and electroimmobilisation under field conditions, and an experiment was conducted with 10 calves, 10 sheep, and 9 pigs, which were equipped with EEG and ECG electrodes, to check the analgesic and other practical effects of the apparatus. The duration of current administration was 20 minutes. Three animals of each species were used as control animals. In all animals, during administration of the current, the breathing movements appeared to be somewhat impaired. The rectal body temperature, the plasma cortisol level, and the pulse rate were raised during the current administration. Moreover, the pulse rate was irregular. The corneal reflex remained positive in all animals, and the reaction to painful stimuli was positive in 15 out of 29 experimental animals. The rectal body temperature, pulse rate, and plasma cortisol level remained constant in the control animals. Before and after administration of the current the electroencephalogram recordings were similar, except in one calf and one sheep, both of which showed patterns suggesting a decreased consciousness. The electrocardiogram recordings showed pronounced changes in cardiac activity. In one pig the heart activity stopped some minutes after the onset of the current. Changes in the electroencephalogram and electrocardiogram were not observed in the control animals during their treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Computer model of the absorption and distribution of colostral immunoglobulins in the newborn calf

The transfer of immunoglobulin (Ig) isotypes (IgG1, IgG2, IgM), gamma-glutamyl transpeptidase (gamma-GT) and added D-xylose from colostrum to serum was investigated in newborn Holstein bull calves. Significant differences were observed in the time courses of the serum concentrations of these colostrum constituents following absorption from pooled colostrum. A computer model was devised to simulate the process of absorption of Ig isotypes, gamma-GT and D-xylose from colostrum in the newborn calf. A Fortran program was used to generate plots of the time course of the concentration of colostrum constituents in serum and other body fluids following a single feed of colostrum. These plots show how the changes in serum concentration of absorbed Ig isotypes, gamma-GT and D-xylose are affected by different rates of intestinal absorption, redistribution in body fluids and removal from plasma. A critical examination of data from the computer model and from the calf feeding experiments supports the view that the absorption of IgG1, IgG2 and IgM is not selective in the calf. The data were compared with earlier studies of the efficiency of the colostral transfer of Ig to the calf. In the present study the transfer efficiencies of IgG1, IgG2, IgM, gamma-GT and D-xylose were 46 per cent, 49 per cent, 47 per cent, 18 per cent and 21 per cent, respectively.     

The excretion of phylloerythrin and bilirubin by calves and sheep.

Under general anaesthesia the common bile duct was ligated in two sheep and two calves. Occlusion of the duct was permanent and was followed by portal fibrosis, proliferation of bile ducts and intrahepatic bile stasis. Mild hepatic cell damage was accompanied by the release of glutamate dehydrogenase, sorbitol dehydrogenase and arginase into serum. The release of gamma-glutamyl transpeptidase was slower but more continuous. One sheep and one calf developed peritonitis associated with the leakage of bile from a biopsy wound in the live. One of these animals and the other two on which biopsy was not performed became photosensitised on exposure to sunlight. The concentration of phylloerythrin was high in serum and urine. All animals became jaundiced and the increased concentration of bilirubin in serum and urine was mainly direct reacting, ie, conjugated with glucuronic acid.     

Acute phase response in horses: changes in plasma cation concentrations after localised tissue injury

An acute phase reaction was elicited in four horses to which Freund's adjuvant was administered intramuscularly. The localised inflammation was accompanied by changes in the plasma concentrations of copper, iron and zinc. The plasma copper concentration, the plasma ceruloplasmin copper concentration and the ceruloplasmin oxidase activity in the plasma steadily increased to a maximum 24 days after the administration of the adjuvant. At this time, the plasma copper concentration was 2.2 micrograms/ml, a 90 per cent increase over the baseline concentration. The ratio of the concentration of plasma ceruloplasmin copper to plasma copper remained constant, indicating that the non-ceruloplasmin bound copper component of the plasma is also an acute phase reactant in the horse. The plasma zinc and iron concentrations decreased to 59 per cent and 30 per cent of their respective baseline concentrations and the severity of the inflammation appeared to influence the plasma concentrations of each metal. Weak correlations between the plasma fibrinogen concentration and the plasma copper and zinc concentrations of 25 horses with plasma fibrinogen concentrations of 5 g/litre or greater indicated that a single measurement of plasma copper concentration is not useful in the diagnosis of non-specific inflammatory disorders of the horse. However, the results suggest that the plasma copper concentrations in serial samples may be used to monitor the resolution of inflammatory disorders in the horse.     

Comparative pharmacokinetics of enrofloxacin in mice, rats, rabbits, sheep, and cows.

OBJECTIVE: To compare pharmacokinetic variables of enrofloxacin (ENR) after IV administration in mice, rats, rabbits, sheep, and cows and to perform allometric analysis of ENR. ANIMALS: 47 mice, 5 rats, 5 rabbits, 5 sheep, and 5 cows. PROCEDURE: Serially obtained plasma samples were assayed for ENR concentration, using high-performance liquid chromatography. In vitro plasma protein binding was determined by ultrafiltration. Plasma ENR concentration versus time curves were fitted by use of nonlinear least-squared regression analysis. Pharmacokinetic variables were correlated further with body weight. RESULTS: In all species studied, the best fit was obtained for a two-compartment open model; ENR half-life ranged from 89 minutes in mice to 169 minutes in cows. Volume of distribution was large in all species studied, with values ranging from 10.5 L/kg in mice to 1.5 L/kg in sheep. Body clearance ranged from 68.1 ml/min/kg for mice to 4.6 ml/min/kg for sheep. Unbound ENR was found to be (mean +/- SD) 58+/-2, 50+/-6, 50+/-2, 31+/-2, and 40+/-3% in plasma of mice, rats, rabbits, sheep, and cows, respectively. The only pharmacokinetic variables that could be correlated with body weight were elimination half-life, clearance, and volume of distribution. Allometric exponents denoting proportionality of half-life, body clearance, and volume of distribution with body weight were 0.06, 0.82, and 0.90, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: An allometric approach could provide a suitable method for determining a scale for ENR pharmacokinetics among various mammalian species. This would faciliatate the administration of appropriate doses of ENR to all animals.     

Pharmacokinetics and pharmacodynamics of dermorphin in the horse

Dermorphin is a μ‐opioid receptor‐binding peptide that causes both central and peripheral effects following intravenous administration to rats, dogs, and humans and has been identified in postrace horse samples. Ten horses were intravenously and/or intramuscularly administered dermorphin (9.3 ± 1.0 μg/kg), and plasma concentration vs. time data were evaluated using compartmental and noncompartmental analyses. Data from intravenous administrations fit a 2‐compartment model best with distribution and elimination half‐lives (harmonic mean ± pseudo SD) of 0.09 ± 0.02 and 0.76 ± 0.22 h, respectively. Data from intramuscular administrations fit a noncompartmental model best with a terminal elimination half‐life of 0.68 ± 0.24 (h). Bioavailability following intramuscular administration was variable (47–100%, n = 3). The percentage of dermorphin excreted in urine was 5.0 (3.7–10.6) %. Excitation accompanied by an increased heart rate followed intravenous administration only and subsided after 5 min. A plot of the mean change in heart rate vs. the plasma concentration of dermorphin fit a hyperbolic equation (simple Emax model), and an EC₅₀ of 21.1 ± 8.8 ng/mL was calculated. Dermorphin was detected in plasma for 12 h and in urine for 48 or 72 h following intravenous or intramuscular administration, respectively.     

Pharmacokinetics and metabolism of dantrolene in horses

Dantrolene is a skeletal muscle relaxant used commonly in performance horses to prevent exertional rhabdomyolysis. The goal of the study reported here was to begin to characterize cytochrome P450-mediated metabolism of dantrolene in the horse and describe the pharmacokinetics of the compound, formulated as a capsule or a compounded paste formulation, following oral administration. Dantrolene is rapidly metabolized to 5-hydroxydantrolene both in vivo and in vitro. Preliminary work with equine liver microsomes suggest that two enzymes are responsible for the metabolism of dantrolene, as evidenced by two distinct K(m) values, one at high and one at low substrate concentrations. For the pharmacokinetic portion of the study, a randomized, balanced 2-way crossover design was employed wherein eight healthy horses received a single oral dose of either capsules or paste followed by a 4 week washout period prior to administration of the second formulation to the same horse. Blood samples were collected at time 0 (prior to drug administration) and at various times up to 96 h postdrug administration. Plasma samples were analyzed using liquid chromatography-mass spectrometry and data analyzed using both noncompartmental and compartmental analysis. Peak plasma concentrations were 28.9 ± 21.6 and 37.8 ± 12.8 ng/mL for capsules and paste, respectively and occurred at 3.8 h for both formulations. Dantrolene and its major metabolite were both below the limit of detection in both plasma and urine by 168 h postadministration.     

Electroanaesthesia or electroimmobilisation of calves,sheep and pigs by the Feenix Stockstill

Summary

Since the end of the last century many investigations with electroanaesthesia have been performed in animals and man. The interest in this method of anaesthesia has emerged because anaesthesia is achieved immediately after the onset of the current and the recovery is very rapid after cutting off of the current. Recently a battery operated apparatus became available (Feenix Stockstill^®) for application of electroanaesthesia and electroimmobilisation under field conditions, and an experiment was conducted with 10 calves, 10 sheep, and 9 pigs, which were equipped with EEG and ECG electrodes, to check the analgesic and other practical effects of the apparatus. The duration of current administration was 20 minutes. Three animals of each species were used as control animals.

In all animals, during administration of the current, the breathing movements appeared to be somewhat impaired. The rectal body temperature, the plasma cortisol level, and the pulse rate were raised during the current administration. Moreover, the pulse rate was irregular. The corneal reflex remained positive in all animals, and the reaction to painful stimuli was positive in 15 out of 29 experimental animals. The rectal body temperature, pulse rate, and plasma cortisol level remained constant in the control animals. Before and after administration of the current the electroencephalogram recordings were similar, except in one calf and one sheep, both of which showed patterns suggesting a decreased consciousness. The electrocardiogram recordings showed pronounced changes in cardiac activity. In one pig the heart activity stopped some minutes after the onset of the current. Changes in the electroencephalogram and electrocardiogram were not observed in the control animals during their treatment.

The results suggest that the apparatus did not cause electroanaesthesia or electrosleep but had mainly an electroimmobilising effect on the experimental animals. Because of the dubious effects on the animals’ welfare, the use of such an apparatus cannot be recommended.     

Pharmacological experiments as a basis for the administration of digoxin in the horse.

It is shown that the concentration of ouabain necessary for 50 per cent inhibition of the Na+K activated membrane ATPase of red cells is similar in man and horse. This is taken to indicate that the two species have similar sensitivity towards cardiac glycosides in general. In five adult healthy horses plasma digoxin concentration was measured with a radioimmunoassay technique after a single intravenous injection of 1 mg/100 kg body weight digoxin. The half time of elimination was 23 h and the apparent volume of distribution 7.3 litres/kg. An approximate estimate of plasma protein binding of digoxin was obtained by measuring digoxin with a fluorimetric assay in the ultrafiltrate from horse plasma containing 2-20 mug/ml. At concentrations below 10(-5)(g/ml 20 to 40 per cent of digoxin present in horse plasma is bound to protein. With this information and by using effective digoxin concentration measured in humans an average daily maintenance dose of 0-5-0-75 mg/100 kg body weight was calculated which may serve as a guideline in the treatment of congestive heart failure with digoxin in the horse.