Pre-analytical stability of sorbitol dehydrogenase in equine heparinized plasma.

Sorbitol dehydrogenase (SDH) activity is one of the most sensitive and specific markers for hepatocellular injury in horses, but its reported lability makes it impractical for use in many clinical settings. To date, stability of SDH in equine samples has only been evaluated in a limited number of studies in serum samples of horses with activities within reference intervals. The objective of the study was to determine pre-analytical stability of equine SDH activity in heparinized plasma stored at different temperatures for up to 72 h. Twenty client-owned horses admitted to a veterinary teaching hospital for any reason were included in the study. Blood samples collected in lithium-heparin tubes were immediately centrifuged and SDH activity was analyzed within 1 h of collection (T0). Aliquots of plasma were stored at room temperature, 4 °C and -20 °C and SDH activity was re-analyzed after 4 h (T4), 24 h (T24) and 72 h (T72). A significant difference from values measured at T0 was found for samples stored at room temperature (P = 0.022) and -20 °C (P < 0.001), but not at 4 °C. The activity of SDH was within ±20% of that measured at T0 for all samples under all temperature conditions stored for 4 h, and for all samples stored at 4 °C for 24 h. Bland-Altman plots revealed narrow limits of agreement at T4 for all storage temperatures and at T24 for samples stored at 4 °C. The mean absolute percentage error and 95th percentile of the absolute percentage error were lower for samples stored at 4 °C than those stored at room temperature or -20 °C. The activity of SDH has adequate stability for 4 h regardless of storage temperature and 24 h if stored at 4 °C across a wide range of values. Knowledge of the pre-analytical stability of SDH may permit its broader use in assessing hepatic disorders in horses.

The Beneficial Radioprotective Effect of Tomato Seed Oil Against Gamma Radiation-Induced Damage in Male Rats.

Radiation protection research receives intense focus due to its significant impact on human health. The present study was undertaken to investigate the protective effect of pretreatment with tomato seed oil (TSO) against gamma radiation-induced damage in rats. Male Wistar rats were divided into four groups: (1) untreated control; (2) TSO-supplemented; (3) gamma-irradiated; (4) TSO-pretreated and gamma-irradiated. Acute exposure of animals to a single gamma radiation dose (6 Gy) induced oxidative stress in major body organs, altered serum lipid homeostasis, significantly increased serum testosterone and sorbitol dehydrogenase levels, and elicited a systemic inflammation as manifested by the induction of serum vascular cell adhesion molecule-1. Oral pretreatment with TSO (1 ml/kg; 3 times/week for 8 weeks) before exposure to gamma radiation protected rats against ionizing radiation-induced oxidative stress, restored lipid homeostasis, and suppressed systemic inflammation. Histological findings of target tissues verified biochemical data. The radioprotective ability of TSO was attributed to its content of phytosterols, policosanol, and antioxidants, including lycopene, ß-carotene, lutein, and tocopherols. TSO is considered a promising radioprotective agent that can be effectively used to protect the body from the damaging effects of harmful radiation.

Effects of S-Allylcysteine on Biomarkers of the Polyol Pathway in Rats with Type 2 Diabetes.

OBJECTIVES: We evaluated the effects of S-allylcysteine (SAC) on biomarkers of the polyol pathway in streptozotocin-nicotinamide (STZ-NA)-induced diabetes in rats. METHODS: Diabetes was induced in male albino Wistar rats by intraperitoneal administration of STZ (55 mg kg-1 bw-1) and NA (110 mg kg-1 bw-1). SAC (150 mg kg-1 bw-1) was orally administered to the rats with diabetes for 45 days to assess its effects on blood glucose, insulin, insulin resistance, glycated hemoglobin, aldose reductase (AR), sorbitol dehydrogenase (SDH), sorbitol, fructose, thiobarbituric acid-reactive substances (TBARS), hydroperoxide, hemoglobin and glutathione (GSH). RESULTS: On SAC administration in the rats with diabetes, the levels of blood glucose, insulin resistance, glycated hemoglobin, AR, SDH, sorbitol, fructose, TBARS and hydroperoxide increased significantly (p<0.05), whereas those of insulin, hemoglobin and GSH decreased. SAC showed therapeutic effects similar to those of gliclazide in decreasing blood glucose, AR, SDH, sorbitol, fructose, glycosylated hemoglobin, TBARS and hydroperoxides levels and significant increases in insulin, hemoglobin and GSH activity in rats with diabetes. Moreover, histopathologic studies also revealed the protective effect of SAC on pancreatic beta cells. CONCLUSIONS: The results indicate that SAC prevents complications of diabetes by reducing the influx of glucose in the polyol pathway, thereby elevating the GSH level and reducing the activities of AR and SDH. Therefore, SAC may have imperative implications for the deterrence and early treatment of type 2 diabetes.

The comparative toxicity of a reduced, crude comfrey (Symphytum officinale) alkaloid extract and the pure, comfrey-derived pyrrolizidine alkaloids, lycopsamine and intermedine in chicks (Gallus gallus domesticus).

Comfrey (Symphytum officinale), a commonly used herb, contains dehydropyrrolizidine alkaloids that, as a group of bioactive metabolites, are potentially hepatotoxic, pneumotoxic, genotoxic and carcinogenic. Consequently, regulatory agencies and international health organizations have recommended comfrey be used for external use only. However, in many locations comfrey continues to be ingested as a tisane or as a leafy vegetable. The objective of this work was to compare the toxicity of a crude, reduced comfrey alkaloid extract to purified lycopsamine and intermedine that are major constituents of S. officinale. Male, California White chicks were orally exposed to daily doses of 0.04, 0.13, 0.26, 0.52 and 1.04 mmol lycopsamine, intermedine or reduced comfrey extract per kg bodyweight (BW) for 10 days. After another 7 days chicks were euthanized. Based on clinical signs of poisoning, serum biochemistry, and histopathological analysis the reduced comfrey extract was more toxic than lycopsamine and intermedine. This work suggests a greater than additive effect of the individual alkaloids and/or a more potent toxicity of the acetylated derivatives in the reduced comfrey extract. It also suggests that safety recommendations based on purified compounds may underestimate the potential toxicity of comfrey.

Evaluation of plasma muscle enzyme activity as an indicator of lesion characteristics and prognosis in horses undergoing celiotomy for acute gastrointestinal pain.

BACKGROUND: In horses undergoing celiotomy for acute gastrointestinal pain, identification of variables correlating with lesion severity and location, and survival provide veterinarians and owners with information that aids in making informed decisions regarding appropriate treatment. Muscle enzyme activity is often increased in horses undergoing celiotomy for acute gastrointestinal pain and it is not known if muscle enzyme activity increase is specific to lesion type or impacts prognosis for survival. The objective of this study was to evaluate the relationship of pre-operative increase in muscle enzyme activities with intestinal lesion characteristics, specifically lesion location (large versus small intestine) and whether it was strangulating versus nonstrangulating, and case survival in horses undergoing celiotomy for acute gastrointestinal pain. METHODS: Records of 241 horses undergoing exploratory laparotomy for colic were reviewed retrospectively. Evaluation of preoperative plasma aspartate aminotransferase (AST), creatine kinase (CK), sorbitol dehydrogenase (SDH), and gamma-glutamyltransferase (GGT) activities, fibrinogen and glucose concentrations, and hematocrit (HCT) and their association with gastrointestinal lesion characteristics and survival was performed. RESULTS: Pre-operative increase in plasma CK and AST activity, and HCT and decrease in plasma bilirubin concentration were significantly associated with presence of lesions resulting in intestinal ischemia. Increase in plasma CK activity and HCT were significantly associated with a decreased probability of survival to hospital discharge. Plasma GGT and SDH activity, and glucose and fibrinogen concentration were not significantly associated with survival or severity of disease in multivariate analysis. CONCLUSIONS: Plasma muscle enzyme activity may be useful as a prognostic indicator in equine colic cases. Given that increases in plasma CK and AST activity were significantly associated with nonsurvival and the presence of intestinal ischemia, preoperative increase in these enzyme activities could assist in identification of disease severity and prognosis of horses undergoing celiotomy for acute gastrointestinal pain. Further study is indicated to elucidate the etiology of increased muscle enzyme activity in horses with surgical colic disease observed in this preliminary study.

D-penicillamine-induced granulomatous hepatitis in brown Norway rats.

The mechanism of idiosyncratic drug reactions (IDRs) remains poorly understood. D-penicillamine treatment is associated with a wide range of autoimmune reactions including liver injury. An animal model which utilizes brown Norway (BN) rats has been used to investigate the mechanism of D-penicillamine-induced IDRs because it mimics the autoimmune reactions that occur in humans. The purpose of this study was to investigate the type of liver injury that results from D-penicillamine treatment in BN rats. We had previously noted that D-penicillamine caused histological changes in the liver, but there was no increase in alanine transaminase (ALT), and we assumed that there was no significant injury. However, we subsequently discovered that D-penicillamine inhibits the ALT assay. In the present study, we found that treatment of BN rats with a low doses of D-penicillamine (10 or 15 mg/day) resulted in a mild increases in glutamate dehydrogenase (GLDH) and sorbitol dehydrogenase (SDH) activities; however, this was not associated with histological changes. A higher dose of D-penicillamine (20 mg/day) resulted in 63% of the rats developing a skin rash, and these rats had elevated serum GLDH and SDH levels with histopathological changes characteristic of granulomatous hepatitis. This included large clusters of leukocytes in the form of granulomas that contained neutrophils, macrophages, and CD8 T cells. These changes did not occur in the rats that did not get sick. This model may be a good model to investigate the characteristics of drug-induced granulomatous hepatitis.

Liver biomarker and in vitro assessment confirm the hepatic origin of aminotransferase elevations lacking histopathological correlate in beagle dogs treated with GABAA receptor antagonist NP260.

NP260 was designed as a first-in-class selective antagonist of α4-subtype GABAA receptors that had promising efficacy in animal models of pain, epilepsy, psychosis, and anxiety. However, development of NP260 was complicated following a 28-day safety study in dogs in which pronounced elevations of serum aminotransferase levels were observed, although there was no accompanying histopathological indication of hepatocellular injury. To further investigate the liver effects of NP260, we assayed stored serum samples from the 28-day dog study for liver specific miRNA (miR-122) as well as enzymatic biomarkers glutamate dehydrogenase and sorbitol dehydrogenase, which indicate liver necrosis. Cytotoxicity assessments were conducted in hepatocytes derived from dog, rat, and human liver samples to address the species specificity of the liver response to NP260. All biomarkers, except ALT, returned toward baseline by Day 29 despite continued drug treatment, suggesting adaptation to the initial injury. In vitro analysis of the toxicity potential of NP260 to primary hepatocytes indicated a relative sensitivity of dog>human>rat, which may explain, in part, why the liver effects were not evident in the rodent safety studies. Taken together, the data indicate that a diagnostic biomarker approach, coupled with sensitive in vitro screening strategies, may facilitate interpretation of toxicity potential when an adaptive event masks the underlying toxicity.

[Activity of the marker liver enzymes under the conditions of toxic hepatitis and alimentary deprivation of protein].

The activity of the sorbitoldehydrogenase (SDH), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in the blood serum of rats with acetaminophen-induced hepatitis under the conditions of alimentary deprivation of protein was studied. The animals were divided into 3 groups: 1--rats with acute acetaminophen-induced hepatitis, maintained on the full ration; 2--rats with acute acetaminophen-induced hepatitis, maintained under the conditions of alimentary deprivation of protein; 3--control. The activity of the sorbitol dehydrogenase in blood serum was determined by the kinetic method, activity of the alanine aminotransferase and alkaline phosphatase - photometrically. It is shown, that in animals with the model hepatitis the activity of sorbitol dehydrogenase in blood serum increases 20-fold, wherein statistical significance between animals with hepatitis maintained under the conditions of full ration and those of low-protein diet is not established. In the group of animals with acetaminophen-induced hepatitis the preservation on the control level of the alkaline phosphatase activity on the base of the increase of alanine aminotransferase by 2.2 times and ratio ALT/ALP>5 testifies about hepatocellular liver injury. In the group of animals with drug-induced hepatitis and alimentary deprivation of protein, the increase of the alkaline phosphatase and alanine aminotransferase activity is observed, herewith the ratio ALT/ALP ranges from 2 to 5 and testifies about mixed liver injury. The conclusion was made, that alimentary deprivation of protein is the critical factor for the development of the disturbances of functional and structural liver integrity, and the therapeutic approaches to the correction of the drug-induced liver injury should be different depending on the value of protein ration in the anamnesis, taking into account the different types of liver injury.

[Squamous cell carcinoma of the reticulum and liver in a Simmental cow]. / Plattenepithelkarzinom in Haube und Leber bei einer Fleckviehkuh.

This report describes an 8.8-year-old Simmental cow with squamous cell carcinoma of the reticulum and liver. The cow had calved recently and was referred to our clinic because of intractable fever, anorexia and progressive indigestion. The general condition and mental status were moderately affected and rectal temperature and respiratory rate were significantly elevated. There were no ruminal sounds and pinching of the withers consistently elicited a grunt. Serum activities of gamma glutamyl transferase, glutamate dehydrogenase and sorbitol dehydrogenase were elevated. Radiographic examination of the reticulum and ultrasonographic examination of the reticulum, liver and abdominal cavity revealed multifocal, poorly demarcated, heterogeneous and echogenic changes in the liver. Biopsy of these lesions yielded a diagnosis of squamous cell carcinoma. The cow was euthanized and a postmortem examination confirmed the diagnosis. A 15 by 15 cm neoplasm was found in the reticular wall, and histological examination showed squamous cell carcinoma. It was assumed that the reticular mass was the primary tumour, which metastasized to the liver via the portal vein.

The effects of heparins on the liver: application of mechanistic serum biomarkers in a randomized study in healthy volunteers.

Heparins have been reported to cause elevations in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) but have not been associated with clinically significant liver injury. The mechanisms underlying these benign laboratory abnormalities are unknown. Forty-eight healthy men were randomized to receive subcutaneous injections of unfractionated heparin (UFH; 150 U/kg), enoxaparin sodium (1 mg/kg), dalteparin sodium (120 IU/kg), or adomiparin sodium (125 IU/kg; a novel heparin) every 12 h for 4.5 days. Asymptomatic elevations in serum ALT or AST were observed in >90% of the subjects. Elevations were also observed in the levels of serum sorbitol dehydrogenase (SDH), glutamate dehydrogenase (GLDH), miR-122, high-mobility group box-1 protein (including the acetylated form), full-length keratin 18, and DNA. Keratin 18 fragments, which are apoptosis biomarkers, were not detected. Biomarker profiles did not differ significantly across heparin treatments. We conclude that heparins as a class cause self-limited and mild hepatocyte necrosis with secondary activation of an innate immune response.

Modification of the metabolism and toxicity of styrene and styrene oxide in hepatic cytochrome P450 reductase deficient mice and CYP2F2 deficient mice.

Styrene causes toxicity in both the lung and the liver. The study of the relationship of this toxicity to the metabolism of styrene has been aided by the use of knockout mice for both bioactivation and detoxification pathways. It has been hypothesized that CYP2E1 is primarily responsible for styrene bioactivation in mouse liver and CYP2F2 in mouse lung. Two knockout strains were used in the current studies. Mice deficient in hepatic cytochrome P450 reductase had much less hepatic metabolism of styrene to styrene oxide. Styrene (600 mg/kg, i.p.) caused significant hepatotoxicity, as determined by serum sorbitol dehydrogenase and glutathione levels, in the wild-type but not in the knockout mice. It caused lung toxicity, as determined by protein levels, cell number, and lactate dehydrogenase activity in the bronchioalveolar lavage fluid of wild-type mice, but this effect was less in the knockout mice. In CYP2F2 knockout mice there was only a small decrease in the hepatic metabolism of styrene but a very large decrease in pulmonary metabolism. As expected the CYP2F2 knockout and wild-type mice were equally susceptible to styrene-induced hepatotoxicity, but the knockout mice were less susceptible to styrene-induced pneumotoxicity. Although the results are inconsistent with the simple hypothesis that styrene pneumotoxicity is due to the bioactivation of styrene to styrene oxide by CYYP2F2, they demonstrate the importance of both liver and lung in the metabolism of styrene, but additional pharmacokinetic studies are needed to help clarify the relationship between target organ metabolism and susceptibility.

Toxicity assessment of individual ingredients of synthetic-based drilling muds (SBMs).

Synthetic-based drilling muds (SBMs) offer excellent technical characteristics while providing improved environmental performance over other drilling muds. The low acute toxicity and high biodegradability of SBMs suggest their discharge at sea would cause minimal impacts on marine ecosystems, however, chronic toxicity testing has demonstrated adverse effects of SBMs on fish health. Sparse environmental monitoring data indicate effects of SBMs on bottom invertebrates. However, no environmental toxicity assessment has been performed on fish attracted to the cutting piles. SBM formulations are mostly composed of synthetic base oils, weighting agents, and drilling additives such as emulsifiers, fluid loss agents, wetting agents, and brine. The present study aimed to evaluate the impact of exposure to individual ingredients of SBMs on fish health. To do so, a suite of biomarkers [ethoxyresorufin-O-deethylase (EROD) activity, biliary metabolites, sorbitol dehydrogenase (SDH) activity, DNA damage, and heat shock protein] have been measured in pink snapper (Pagrus auratus) exposed for 21 days to individual ingredients of SBMs. The primary emulsifier (Emul S50) followed by the fluid loss agent (LSL 50) caused the strongest biochemical responses in fish. The synthetic base oil (Rheosyn) caused the least response in juvenile fish. The results suggest that the impact of Syndrill 80:20 on fish health might be reduced by replacement of the primary emulsifier Emul S50 with an alternative ingredient of less toxicity to aquatic biota. The research provides a basis for improving the environmental performance of SBMs by reducing the environmental risk of their discharge and providing environmental managers with information regarding the potential toxicity of individual ingredients.

Recommendations to qualify biomarker candidates of drug-induced liver injury.

Certain compounds that induce liver injury clinically are not readily identified from earlier preclinical studies. Novel biomarkers are being sought to be applied across the pharmaceutical pipeline to fill this knowledge gap and to add increased specificity for detecting drug-induced liver injury in combination with aminotransferases (alanine and aspartate aminotransferase)--the current reference-standard biomarkers used in the clinic. The gaps in the qualification process for novel biomarkers of regulatory decision-making are assessed and compared with aminotransferase activities to guide the determination of safe compound margins for drug delivery to humans where monitoring for potential liver injury is a cause for concern. Histopathologic observations from preclinical studies are considered the principal reference standard to benchmark and assess subtle aminotransferase elevations. This approach correlates quite well for many developmental compounds, yet cases of discordance create dilemmas regarding which standard(s) indicates true injury. Concordance amongst a broader set of biomarker injury signals in a qualification paradigm will increase confidence, leading to accepted and integrated translational biomarker signals during safety assessment processes across the pharmaceutical industry, with academia, in government and in contractor laboratories.

Effects of synthetic androgens on liver function using the rabbit as a model.

The objective of this study was to determine whether the rabbit was a suitable model to test new synthetic androgens for potential liver toxicity within a short dosing interval. Adult male rabbits were dosed orally daily on days 0-13 with 17α-methyltestosterone (MT) as a positive control and testosterone (T) as a negative control to validate this model. Synthetic androgens tested were: 7α-methyl-19-nortestosterone (MENT), dimethandrolone-undecanoate (DMAU), and 11ß-methyl-19-nortestosterone-17ß-dodecylcarbonate (11ß-MNTDC). Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma glutamyl transpeptidase (GGT), and sorbitol dehydrogenase (SDH), as well as clearance of intravenous injected bromsulfonphthalein (BSP) from serum on days 0, 7, and 14, were determined. As expected, T (10 mg/kg/d) did not adversely affect BSP retention or serum liver enzymes. MT (10 mg/kg/d) increased BSP retention, and AST, ALT, GGT, and SDH levels, indicating that this model could detect androgens known to be hepatotoxic. DMAU and MENT (10 mg/kg/d) increased BSP retention and all 4 serum liver enzymes as well, but the effects were less than those observed with MT at the same dose. All parameters returned to baseline 2 weeks after cessation of dosing. 11ß-MNTDC at 10 mg/kg/d did not have an effect on BSP retention or liver enzymes, but a slight increase in serum GGT levels was observed in rabbits treated with 25 mg/kg/d. For the androgens that exhibited liver toxicity at 10 mg/kg/d (MT, DMAU, and MENT), a no-observed-effect level of 1 mg/kg/d was established. Overall ranking of the synthetic androgens from most to least hepatotoxic on the basis of percent BSP retention was: MT & DMAU > MENT > 11ß-MNTDC. Hence, the rabbit appears to be a promising model for detection of potential liver toxicity by synthetic androgens using BSP clearance and serum liver enzyme levels as early indicators of injury.

Assessment of biological effects of pollutants in a hyper eutrophic tropical water body, Lake Beira, Sri Lanka using multiple biomarker responses of resident fish, Nile tilapia (Oreochromis niloticus).

Biomarkers measured at the molecular and cellular level in fish have been proposed as sensitive "early warning" tools for biological effect measurements in environmental quality assessments. Lake Beira is a hypertrophic urban water body with a complex mixture of pollutants including polycyclic aromatic hydrocarbons (PAHs) and Microcystins. In this study, a suite of biomarker responses viz. biliary fluorescent aromatic compounds (FACs), hepatic ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST), brain and muscle cholinesterases (ChE), serum sorbitol dehydrogenase (SDH), and liver histology of Oreochromis niloticus, the dominant fish inhabiting this tropical Lake were evaluated to assess the pollution exposure and biological effects. Some fish sampled in the dry periods demonstrated prominent structural abnormalities in the liver and concomitant increase in serum SDH and reduction in hepatic GST activities in comparison to the control fish and the fish sampled in the rainy periods. The resident fish with apparently normal liver demonstrated induction of hepatic EROD and GST activities and increase in biliary FACs irrespective of the sampling period indicating bioavailability of PAHs. Muscle ChE activities of the resident fish were depressed significantly indicating exposure to anticholinesterase substances. The results revealed that fish populations residing in this Lake is under threat due to the pollution stress. Hepatic abnormalities in the fish may be mainly associated with the pollution stress due to recurrent exposure to PAHs and toxigenic Microcystis blooms in the Lake.

Alteration in metabolism and toxicity of acetaminophen upon repeated administration in rats.

Our previous studies showed that administration of a subtoxic dose of acetaminophen (APAP) to female rats increased generation of carbon monoxide from dichloromethane, a metabolic reaction catalyzed mainly by cytochrome P450 (CYP) 2E1. In this study we examined the changes in metabolism and toxicity of APAP upon repeated administration. An intraperitoneal dose of APAP (500 mg/kg) alone did not increase aspartate aminotransferase, alanine aminotransferase, or sorbitol dehydrogenase activity in serum, but was significantly hepatotoxic when the rats had been pretreated with an identical dose of APAP 18 h earlier. The concentrations and disappearance of APAP and its metabolites in plasma were monitored for 8 h after the treatment. APAP pretreatment reduced the elevation of APAP-sulfate, but increased APAP-cysteine concentrations in plasma. APAP or APAP-glucuronide concentrations were not altered. Administration of a single dose of APAP 18 h before sacrifice increased microsomal CYP activities measured with p-nitrophenol, p-nitroanisole, and aminopyrine as probes. Expression of CYP2E1, CYP3A, and CYP1A proteins in the liver was also elevated significantly. The results suggest that administration of APAP at a subtoxic dose may result in an induction of hepatic CYP enzymes, thereby altering metabolism and toxicological consequences of various chemical substances that are substrates for the same enzyme system.

Correlation of virus and host response markers with circulating immune complexes during acute and chronic woodchuck hepatitis virus infection.

Woodchuck hepatitis virus (WHV) is an established model for human hepatitis B virus. The kinetics of virus and host responses in serum and liver during acute, self-limited WHV infection in adult woodchucks were studied. Serum WHV DNA and surface antigen (WHsAg) were detected as early as 1 to 3 weeks following experimental infection and peaked between 1 and 5 weeks postinfection. Thereafter, serum WHsAg levels declined rapidly and became undetectable, while WHV DNA levels became undetectable much later, between 4 and 20 weeks postinfection. Decreasing viremia correlated with transient liver injury marked by an increase in serum sorbitol dehydrogenase (SDH) levels. Clearance of WHV DNA from serum was associated with the normalization of serum SDH. Circulating immune complexes (CICs) of WHsAg and antibodies against WHsAg (anti-WHs) that correlated temporarily with the peaks in serum viremia and WHs antigenemia were detected. CICs were no longer detected in serum once free anti-WHs became detectable. The detection of CICs around the peak in serum viremia and WHs antigenemia in resolving woodchucks suggests a critical role for the humoral immune response against WHsAg in the early elimination of viral and subviral particles from the peripheral blood. Individual kinetic variation during WHV infections in resolving woodchucks infected with the same WHV inoculum and dose is likely due to the outbred nature of the animals, indicating that the onset and magnitude of the individual immune response determine the intensity of virus inhibition and the timing of virus elimination from serum.

Hepatic metabolism of contaminants in the terapontid fish, yellowtail trumpeter (Amniataba caudavittata Richardson).

The yellowtail trumpeter (Amniataba caudavittata) is an estuarine-dependent omnivorous fish found in the Swan-Canning Estuary, Western Australia. Thirty five fish were injected with either the polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P), the synthetic flavenoid beta-naphthoflavone (BNF), or used as controls. The fish were then sampled at 3 and 7 days postinjection. Induction of the enzyme ethoxyresorufin O-deethylase (EROD) activity was nonsignificant while ethoxycoumarin O-deethylase (ECOD) activity induction differed amongst treatments. A high interindividual variability in the EROD activity was observed. The measurement of sorbitol dehydrogenase in the serum (s-SDH) was elevated (BNF 2.2 times and B[a]P 3.2 times the control fish) demonstrating that liver cell damage had occurred. Increases in biliary metabolites of both B[a]P-type and pyrene-type (19 times and 3.4 times the controls respectively) indicated that detoxification of pyrene-type compounds had taken place. Fish of the Terapontidae family, such as the yellowtail trumpeter, were found to be suitable for biomonitoring the health of the Swan-Canning Estuary. A combination of ECOD activity, s-SDH, and the measurement of biliary metabolites represents a suitable suite of biomarkers for environmental monitoring of the sublethal effects of PAH pollution in these fish.

Induction of hepatic CYP2E1 by a subtoxic dose of acetaminophen in rats: increase in dichloromethane metabolism and carboxyhemoglobin elevation.

Dichloromethane (DCM) is metabolically converted to carbon monoxide mostly by CYP2E1 in liver, resulting in elevation of blood carboxyhemoglobin (COHb) levels. We investigated the effects of a subtoxic dose of acetaminophen (APAP) on the metabolic elimination of DCM and COHb elevation in adult female rats. APAP, at 500 mg/kg i.p., was not hepatotoxic as measured by a lack of change in serum aspartate aminotransferase, alanine aminotransferase, and sorbitol dehydrogenase activities. In rats pretreated with APAP at this dose, the COHb elevation resulting from administration of DCM (3 mmol/kg i.p.) was enhanced significantly. Also blood DCM levels were reduced, and its disappearance from blood appeared to be increased. Hepatic CYP2E1-mediated activities measured with chlorzoxazone, p-nitrophenol, and p-nitroanisole as substrates were all induced markedly in microsomes of rats treated with APAP. Aminopyrine N-demethylase activity was also increased slightly, but significantly. Western blot analysis showed that APAP treatment induced the expression of CYP2E1 and CYP3A proteins. Neither hepatic glutathione contents nor glutathione S-transferase activity was changed by the dose of APAP used. The results indicate that, contrary to the well known hepatotoxic effects of this drug at large doses, a subtoxic dose of APAP may induce CYP2E1, and to a lesser degree, CYP3A expression. This is the first report that APAP can increase cytochrome P450 (P450)-mediated hepatic metabolism and the resulting toxicity of a xenobiotic in the whole animal. The pharmacological/toxicological significance of induction of P450s by a subtoxic dose of APAP is discussed.

Serum bile acids concentrations in healthy and clinically ill neonatal foals.

BACKGROUND: Reference ranges for serum bile acids (SBA) concentration are well established in healthy adult horses. Increased values are indicative of hepatic disease. HYPOTHESES: SBA concentrations are significantly greater in the neonatal period compared with mature horses, and illness in the neonatal period will further increase SBA. ANIMALS: Ten healthy mature horses, 12 healthy foals, and 31 clinically ill foals. METHODS: Prospective cross-sectional study. Blood samples were obtained once from the mature horses, from healthy foals immediately after birth, at 2 days, and at 1, 2, 3, 4, and 6 weeks of age; and from ill foals less than 1 month of age at the time of admission to the Veterinary Teaching Hospital. SBA concentrations were determined enzymatically and by radioimmunoassay. Total and direct bilirubin and triglyceride concentrations were measured, as well as sorbitol dehydrogenase (SDH) and gamma-glutamyltransferase (GGT) activities. RESULTS: There was a significant negative correlation between age and SBA concentration. Compared with mature horses, SBA concentrations were significantly greater in healthy foals at each collection time over the first 6 weeks of life. Radioimmunoassay values were lower than enzymatic SBA values, with increasing bias as the mean difference between values increased. When comparing age-matched values between healthy and ill foals, there were no significant differences in SBA. None of the ill foals had a primary diagnosis of hepatic disease. There was no significant correlation between the SBA concentration and the bilirubin or triglyceride concentrations or the GGT activity. There was a significant direct correlation between increased SBA and serum SDH activity in healthy foals only. CONCLUSION AND CLINICAL IMPORTANCE: SBA concentrations in foals are significantly higher in the early neonatal period, underscoring the importance of using age-matched references when evaluating clinical pathology values during the neonatal period.