Liver function in horses encompasses a range of physiological processes essential for maintaining homeostasis. The liver is responsible for various metabolic, detoxification, and synthetic activities, including the metabolism of carbohydrates, proteins, and fats, as well as the detoxification of endogenous and exogenous substances. It also synthesizes proteins such as albumin and clotting factors, and produces bile necessary for digestion. Liver function can be assessed through biochemical tests that measure enzyme activities and metabolite levels in the blood. This page compiles peer-reviewed research studies and scholarly articles that explore the mechanisms, assessment, and clinical implications of liver function in equine health.
Norby MA, Link RP.Thirty horses were anaesthetized with halothane and thiopental sodium. To determine the hepatotoxic effect of halothane, bromsulphalein (BSP) tests for liver function were made immediately before and 24 hours after anaesthesia and surgery. The periods of anaesthesia varied from 35 minutes to 3 1/2 hours. Results of these tests indicated no significant impairment of liver function 24 hours after anaesthesia, the time at which liver damage due to chloroform, which has a molecular structure similar to that of halothane, has reached its peak
Corrêa WM, Nilsson MR.Five livers of equine fetuses, aborted due to the action of equine abortion virus, five livers from men, two of whom died of epidemic hepatitis and three obtained by needle biopsies, 5 livers of dogs with infectious canine hepatitis and 7 livers of ducklings that had hepatitis, were studied histopathologically. The foals' livers were studied by several staining methods and the others by H. E. only. The results indicate that the lesions are quite similar in the four species with the appearance of nuclear inclusion bodies only in foals and dogs. The strong staining properties of the nuclear incl...
Rodriguez JY, Finneburgh BM, Lewis BC, Flanagan J, Snowden KF.Heterobilharzia americana is a trematode parasite (family: Schistosomatidae) of mammalian wildlife that occasionally infects domestic dogs and horses in the southeastern United States. This report presents the first case of H. americana infection in a Grant's zebra (Equus burchelli boehmi). The parasite was diagnosed post mortem as an incidental finding by histopathologic identification of H. americana eggs in the liver parenchyma after the zebra succumbed in an accidental traumatic death. Molecular analysis of a portion of the parasite small subunit ribosomal RNA gene demonstrated 100% identi...
van der Merwe D, van den Wollenberg L, van Hees-Valkenborg J, de Haan T, van der Drift S.We determined reference intervals (RIs) for concentrations of trace minerals and toxic elements based on liver samples from 122 apparently healthy horses at 2 slaughter facilities in the Netherlands. Samples were collected during the spring and fall of 2021, and the sex and age of the horses were registered upon sampling. Concentrations of arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel, selenium, vanadium, and zinc were measured in liver samples using inductively coupled plasma-mass spectrometry (ICP-MS) after nitric acid digestion. RIs were calculated us...
Tulleners EP, Becht JL, Richardson DW, Divers TJ.Obstructive choledocholithiasis in a 12-year-old mare was corrected surgically by choledocholithotripsy. The mare had a history of chronic weight loss, intermittent fever, partial anorexia, jaundice, recurrent abdominal pain, and an abdominal mass palpable per rectum. Values for alkaline phosphatase, bilirubin, gamma-glutamyl transferase, sorbitol dehydrogenase, and bromsulpthalein half-life were increased and bilirubinuria was evident before surgery. Two liver biopsies revealed periportal and portal fibrosis, bile duct proliferation, cholestasis, and variable amounts of hepatocellular necrosi...
Charleston W, McKenna P.Abstract A general review of the epidemiology, significance and control of nematode parasitism of sheep, goats, cattle and deer in New Zealand, the emergence of anthelmintic resistance and its effects, and the search for parasite control strategies that reduce reliance on anthelmintic use, is provided. The research that has formed the basis for present levels of understanding of this complex and important topic is summarised and sources of further information are indicated. Aspects of nematode infections of horses, pigs, dogs and cats, and the history of the liver fluke, Fasciola hepatica, in ...
Kovár J, Dürrová E, Skurský L.The interactions of three groups of probes (berberine alkaloids, tricyclic psychopharmaca and acridine derivatives) with isoenzymes of horse liver alcohol dehydrogenase and with rat liver alcohol dehydrogenase have been examined. These compounds inhibit the activity of the EE isoenzyme of horse liver alcohol dehydrogenase but differ in their behaviour towards the steroid-active enzymes (i.e. the ES isoenzyme of horse liver alcohol dehydrognase and alcohol dehydrogenase from rat liver): psychopharmaca inhibit, acridines activate and berberines do not bind. The ligands differ also in their influ...
Dyke TM, Sams RA, Hinchcliff KW.To measure renal clearance of antipyrine and urinary excretion of antipyrine (AP) metabolites in horses by use of validated high-performance liquid chromatography (HPLC) methods. Methods: 8 Standardbred mares. Methods: HPLC methods for measurement of AP in equine plasma and AP and its metabolites in equine urine were validated. Antipyrine (20 mg/kg of body weight) was administered i.v., and blood samples and urine specimens were collected over 24 hours. Results: Median plasma clearance of AP in horses was 6.2 ml/min/kg, of which < 2% could be attributed to renal clearance. Urinary excretion...
Gee EK, Firth EC, Morel PC, Fennessy PF, Grace ND, Mogg TD.To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dam's age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age. Methods: Thirty-th...
Pearson EG.Of 41 equids referred to a veterinary teaching hospital in the Pacific northwest because of dyspnea and inspiratory noise, 3 ponies were diagnosed as having liver failure, most likely attributable to pyrrolizidine alkaloid toxicosis. Dyspnea appeared to be caused by laryngeal and/or pharyngeal paralysis. It is proposed that this paralysis was a manifestation of hepatic encephalopathy. Although these clinical signs are not common for pyrrolizidine toxicosis, practitioners should be aware of the possibility so that misdiagnosis of other causes of inspiratory dyspnea may not be made.
Rostang A, Desjardins I, Espana B, Panzuti P, Berny P, Prouillac C, Pin D.This study aimed to investigate both the pharmacokinetic behavior and tolerance of methotrexate (MTX) in horses to design a specific dosing regimen as a new immunomodulatory drug for long-term treatment. To determine the primary plasma pharmacokinetic variables after single intravenous, subcutaneous or oral administration, six horses were administered 0.3 mg/kg MTX in a crossover design study. After a 10-week washout, MTX was administered subcutaneously to three of the six previously treated horses at a dose of 0.3 mg/kg once per week for 3 months. In both studies, MTX and metabolite concen...
Bracher V, Steiger R, Huser S.In the present study the breath hydrogen (H2) excretion test was combined with the xylose absorption test in 4 normal horses and 9 clinical patients with chronic diarrhea (n = 3) or chronic weight loss without diarrhea (n = 6). All horses underwent a thorough clinical examination. Laboratory evaluations consisted of haematology and serum biochemistry as well as bacteriological and parasitological examination of feces. In addition, serum electrophoresis and abdominocentesis was performed in all the clinical patients. Gastroscopy was carried out in 6 patients and rectal biopsies were obtained fr...
Owen M, Ferjak EN, Cavinder CA, McCarty KJ, Yankey KC, Hart CG, Burnett DD, Dinh T, Lemley CO.The objective of this study was to determine the activity of steroid- and eicosanoid-metabolizing enzymes in horses with varying BCSs. The BCSs of twenty non-pregnant, anoestrous mares were determined prior to euthanasia, and tissue samples were collected from the liver, kidney, adrenal gland, ovary and endometrium. Cytochrome P450 1A (CYP1A), 2C (CYP2C), 3A (CYP3A) and uridine 5'-diphospho-glucuronosyltransferase (UGT) activities were determined using luminogenic substrates. The MIXED procedure of SAS was used to test the effect of BCS on enzyme activity and differences between tissues. Activ...
Taylor SD, Kritchevsky JE, Huang P, Olave C, Waxman SJ, Miller MA.To report history, clinical examination findings, clinicopathologic findings, diagnostic test results, treatment, and outcome in horses with a novel idiopathic hepatitis syndrome. 13 client-owned horses. Medical records of horses that were presented with fever and increased blood liver enzyme activity over a 16-month period were reviewed (December 1, 2020, to April 1, 2022). Collected data included signalment, history, clinical and clinicopathologic findings, diagnostic test results, treatment, clinical progression, and short-term outcome. Affected horses were presented between December and Ap...
Bastianello SS, Nesbit JW.The pathological features of biliary atresia in a foal are described. A 4-week-old American Saddler foal was presented for autopsy following an illness characterised by clinical features indicative of hepatic failure. The significant macroscopical lesions occurred in the liver which was extremely enlarged, mottled in appearance and indurated. Bile stasis was evident. Lobular distinction was absent and on sectioning, large bile ducts were absent. A moderate ascites, hydrothorax and hydropericardium and a mild anasarca and intermuscular oedema accompanied the hepatic lesion. The diagnosis of bil...
Gu XL, Dai FY, Xiao X, Li GZ, Zhang LM, Qu WJ.The effect of Ageratina adenophora on pathological characteristics of the liver and lungs as well as serum biochemical parameters in horses were investigated. Ten horses without ingestion history of Ageratina adenophora were classified into the control group, and 10 poisoned but survived horses with 3 months ingestion history were set as the case group. Results showed that serum AST, ALT, ALP, magnesium and phosphorus were elevated significantly, while creatinine was decreased remarkably. Hematoxylin and eosin staining of liver tissues showed diffuse swelling or destruction of hepatocytes, nar...
Hayami A, Darwish WS, Ikenaka Y, Nakayama SM, Ishizuka M.There is little information about drug metabolism and pharmacokinetics in horses. Therefore, it is necessary to characterize the profiles of drug metabolites for the safe use of drugs. In this study, we focused on cytochrome P450 enzymes (CYPs), which represent an important enzyme group to determine pharmacological effects of drugs. We chose diazepam as the drug of choice for this study. The aim of this study was to elucidate the metabolic pathway of diazepam in horses in comparison with rats, and to clarify CYP subfamilies responsible for diazepam metabolism in horses. Our results showed tema...
Godber LM, Brown CM, Mullaney TP.A 13-year-old American Saddlebred mare was presented with a 4-day history of anorexia. Physical examination revealed increased inspiratory effort and bony enlargement of the distal limbs. Radiographs indicated a thoracic mass and periosteal proliferations on the distal limbs consistent with hypertrophic osteopathy. Gastric endoscopy revealed distal esophageal and gastric ulceration, and functional pyloric stenosis. Abdominal ultrasonographic examination revealed multiple large, cystic structures associated with the liver. A percutaneous biopsy indicated the thoracic mass to be a granular cell ...
Ho EN, Kwok WH, Leung DK, Wan TS, Wong AS.Turinabol (4-chloro-17alpha-methyl-17beta-hydroxy-1,4-androstadien-3-one) is a synthetic oral anabolic androgenic steroid. As in the case of other anabolic steroids, it is a prohibited substance in equine sports. The metabolism of turinabol in human has been reported previously; however, little is known about its metabolic fate in horses. This paper describes the studies of both the in vitro and in vivo metabolism of turinabol in racehorses with an objective to identify the most appropriate target metabolites for detecting turinabol administration. For the in vitro studies, turinabol was incub...
Sweeney RW, Sweeney CR, Saik J, Lichtensteiger CA.Chronic granulomatous bowel disease was diagnosed in 3 sibling Standardbred horses. Clinical signs included weight loss, loose feces, and decreased appetite in the terminal stage of the disease. Abnormal laboratory findings included hypoproteinemia and low xylose absorption. Necropsy revealed granulomatous inflammation of the intestines, mesenteric lymph nodes, and liver. Eosinophilic infiltration of the granulomatous lesions was a prominent finding in one horse. A causative agent was not detected by special histochemical staining or bacteriologic culturing.
Komori M, Higami A, Imai Y, Imaoka S, Funae Y.A form of P450 [termed P450(h-1)] was purified from the liver microsomes of a male horse to electrophoretic homogeneity. The specific content of the final P450(h-1) preparation was 14.8 nmol/mg of protein and the recovery was 0.38% of the microsomal P450. The apparent molecular weight of P450(h-1) was 52,000 Da. The absorption spectra of P450(h-1) indicated that P450(h-1) was a low- and high-spin mixed type P450 in the oxidized form. The reconstituted system containing P450(h-1) could catalyze benzphetamine N-demethylation, 7-ethoxycoumarin O-deethylation, and testosterone 16 alpha-hydroxylati...
Needles RK, Dubois MS.This case report documents an unusual case of persistent colic in a horse caused by an anomalous vascularized band of tissue running between the visceral surface of the liver and the mesentery of the large colon at the level of the sternal/diaphragmatic flexures. The horse was presented with a history of exhibiting signs of mild persistent colic that were suspected to be caused by displacement of the large colon. Volvulus of the large colon was identified during exploratory celiotomy. The band of tissue was transected, and the displacement corrected. The horse made an uneventful recovery. Trai...
Valieva TA, Valiev AG, Kulakova SN, Levachev MM.During six weeks rats were given a ration containing, as the only source of fat, lipids of sublimated mare's milk that had been stored with or without antioxidants (quercitrol, bisalcophen) during 3 months. The influence of specific quality of the ration fat on lipids and fatty acid composition of lipids in blood plasma, erythrocytic stroma and liver tissue, as well as on lipid peroxidation in the tissues was studied in the test animals. No changes induced by the lipids from sublimated mare's milk were detected in the parameters studied.
Estrada R, Chaves F, Robles A, Rojas E, Segura E, Gutiérrez JM.Blood components were studied in six horses immunized with snake venoms for the production of polyvalent antivenom in Costa Rica. No significant changes in hemoglobin or hematocrit throughout the immunization period were observed, whereas a significant increment in total serum proteins occurred in the second half of the immunization process, probably due to an increased synthesis of immunoglobulins. There were no significant changes in creatine kinase, but a slight increment was detected in both transaminases, although they did not exceed normal limits. These findings suggest the absence of re...
Cutler C, White DL, Viljanto M.SR-9009 is a synthetic compound widely available to purchase online as 'supplement' products due to its potential performance-enhancing effects, presenting a significant threat with regard to doping control in sport. In vitro metabolism with equine liver microsomes was performed to identify potential targets for detection of SR-9009. Six metabolites were identified, with the most abundant consisting of N-dealkylated metabolites (M1-M3). The addition of the identified metabolites to high-resolution accurate mass databases resulted in a positive finding for the N-dealkylated metabolite M1 of SR-...
Cutler C, Viljanto M, Taylor P, Hincks P, Biddle S, Van Eenoo P.Selective androgen receptor modulators, SARMs, are a large class of compounds developed to provide therapeutic anabolic effects with minimal androgenic side effects. A wide range of these compounds are available to purchase online and thus provide the potential for abuse in sports. Knowledge of the metabolism of these compounds is essential to aid their detection in doping control samples. In vitro models allow a quick, cost-effective response where administration studies are yet to be carried out. In this study, the equine phase I metabolism of the non-steroidal SARMs GSK2881078, LGD-2226, LG...
Poonacha KB, Donahue JM, Giles RC, Hong CB, Petrites-Murphy MB, Smith BJ, Swerczek TW, Tramontin RR, Tuttle PA.Leptospirosis was diagnosed in 51 equine fetuses and 16 stillborn foals with gestational ages from 3 1/2 to 11 months. Diagnosis was based on one or more of the following: positive fetal antibody titer, positive fluorescent antibody test, demonstration of spirochetes in kidney and/or placental sections stained by the Warthin-Starry technique, high leptospiral titers in aborting mares, or isolation of Leptospira spp. from fetal organs. Gross lesions were observed in 80.3% of the fetuses, stillborn foals, and placentas. Gross placental lesions included nodular cystic allantoic masses, edema, are...
Johnstone IB, Petersen D, Crane S.Plasma Antithrombin III (ATIII) activity was quantitated in 24 clinically normal Standardbred/Thoroughbred horses using a clotting time technique. ATIII activity ranged from 80 to 106% of the pooled reference standard plasma, with a mean of 94%. Horses presenting with impaction or spasmotic colic (n=17) had normal plasma ATIII activity, while 15 horses presenting with acute diarrhea/colitis had significantly lower plasma ATIII activity with a mean of only 74% of the reference plasma. Seven horses presenting with liver disease had significantly higher plasma ATIII activity with a range of 127 t...
Maly IP, Sasse D.Microquantitative measurements of ADH-activity were carried out on the livers of male and female rats, guinea-pigs and horses (two geldings and a mare). Lyophilized cryostat sections of liver parenchyma were microdissected the whole way along the sinusoidal length from the terminal afferent vessels to the terminal efferent venule. ADH activity in samples of about 50-150 ng was measured in a microbiochemical assay using the oil-well technique without enzymatic cycling, by direct luminometric determination of NADH. On the basis of the single measurements, mean values of total hepatic ADH activit...
Kimble KM, Gomez G, Szule JA, Dubey JP, Buchanan B, Porter BF.An adult American Quarter Horse gelding with a history of weight loss presented with an acute onset of colic, fever, soft faeces and elevated liver enzymes. At necropsy, there were gastric mucosal masses and evidence of caecal necrosis. Histologically, the masses were lymph nodes with granulomatous inflammation and areas of liquefactive necrosis. Within and surrounding necrotic areas were free and intrahistiocytic clusters of protozoal tachyzoites. Similar but milder inflammation was evident in the spleen, lungs and liver. Necrotizing typhlitis was also evident. Immunolabelling for Toxoplasma ...
Guan M, Dai D, Li L, Wei J, Yang H, Li S, Zhang Y, Lin Y, Xiong S, Zhao Z.High levels of triacylglycerols (TGs) have been linked to cardiovascular disease and liver diseases. Comprehensively analyzing TGs is helpful to understand the TGs functions in these diseases. However, due to the existence of a large number of isomers TGs and the lack of commercial standards, precise analysis of individual triacylglycerol (TG) with specific fatty acid chain composition is full of challenge. In this work, ultra-performance liquid chromatography (UPLC) coupled with electrospray ionization (ESI) mass spectrometry (MS) were employed for comprehensive qualification and quantificati...
Leblová S, Galociová J, Cerovská N.The studied herbicides (terbutylazine, simazine) inhibit the activity of plant, animal, and yeast alcohol dehydrogenases. The inhibition constant Ki for alcohol dehydrogenase (ADH) isolated from peas and bakers' yeast equals approximately 10(-4) M, and that for ADH isolated from horse liver is of the order of 10(-5) M. The character of inhibition for all the herbicides studied for the reaction catalyzed by pea, liver, and yeast ADH is always noncompetitive toward ethanol and competitive with respect to NAD. The inhibition constants for the enzyme isolated from peas are pH independent. The inte...
