Observations of alanine aminotransferase and aspartate aminotransferase in THRIVE studies treated orally with ximelagatran

Treatment of acute venous thromboembolism (VTE) and prophylaxis of recurrent events has been investigated in the THRIVE (THRombin Inhibitor in Venous Thrombe Embolism) Treatment and the THRIVE III trial using the oral direct thrombin inhibitor ximelagatran. Alanine aminotransferase (ALAT) increased in 9.6% and 6.4% of patients in the THRIVE Treatment and THRIVE III trials, respectively. The authors analysed the time course of the ALAT and in additionally of aspartate aminotransferase (ASAT) in blood from 52 and 23 patients participating in the THRIVE Treatment and the THRIVE III trials in Germany. Analysis of variance for repeated measures and t test were performed. In the THRIVE Treatment trial, ALAT was significantly higher at week 2 for enoxaparin/warfarin (p => .0039, t test) and at months 3 and 6 for ximelagatran (p = .0453, p = .0014, respectively). ASAT and ASAT/ALAT ratio values did not increase and not differ for both groups. In the THRIVE III trial, ALAT and ASAT did not increase and did not differ compared to the comparator placebo. 2 x 36 mg Ximelagatran, induced higher ALAT values at months 3 and 6 compared to 2 x 24 mg ximelagatran (p = .0105, p = .0063, respectively). ASAT did not differ between the two doses of ximelagatran. The ASAT/ALAT ratios were lower at week 2 for enoxaparin/warfarin (t-test, p = .0032) and at month 3 and 6 for 2 x 36 mg versus warfarin or 2 x 24 mg Ximelagatran (p between .0187 and .0002). The authors conclude that ALAT increases dose dependently during therapy with ximelagatran. The less frequent and lower increase of ASAT values compared to ALAT values indicates a nontoxic effect of ximelagatran on liver cells.     

Biochemical Changes Induced in Liver and Serum of Diplodiatoxin (Stenocarpella maydis) Treated Male and Female Rats

Abstract

Present study was conducted to investigate the acute and sub-acute toxic effect of diplodiatoxin with special reference to biochemical membrane bound enzymes like aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and RBC acetylcholinesterase (AChE) in male and female rats. For acute study, rats were treated with a single oral dose of 5.7 mg/kg of diplodiatoxin, whereas for sub-acute study, the rats received 0.27 mg/kg/day for 21 days. Acute and sub-acute diplodiatoxin treatment caused loss in body weight and feed intake along with symptoms including irritation, dullness, tremors and convulsions. Diplodiatoxin caused a significant increase in serum ASAT and ALAT and a decrease in activity in the liver in both acute and sub-acute studies. This compound also significantly inhibited RBC AChE. Sexual dimorphism was observed when male rats were compared with female rats (p<0.05). The enzyme alterations observed in the affected enzymes recovered to the normal levels by day 7 post treatment (withdrawal study) in both acute and sub-acute treated rats. A negative correlation was observed with regard to these enzymes when serum was compared with liver. These enzyme profiles show increases in serum with parallel decrease in liver, indicating necrosis of liver. These results suggest that diplodiatoxin has potential to affect hepatic end-points.     

Renal cysteine conjugate C-S lyase mediated toxicity of halogenated alkenes in primary cultures of human and rat proximal tubular cells

Proximal tubular cells from human (HPT) and rat (RPT) kidneys were isolated, grown to confluence and incubated with S-(1,2-dichlorovinyl)- l-cysteine (DCVC), S-(1,2,2-trichlorovinyl)- l-cysteine (TCVC), S-(1,1,2,2-tetrafluoroethyl)- l-cysteine (TFEC) and S-(2-chloro-1,1-difluorethyl)- l-cysteine (CDFEC), the cysteine conjugates of nephrotoxicants. The cultures were exposed to the conjugates for 12, 24 and 48 h and the toxicity determined using the MTT assay. All four conjugates caused dose-dependent toxicity to RPT cells over the range 50-1,000 microM, the order of toxicity being DCVC>TCVC>TFEC=CDFEC. The inclusion of aminooxyacetic acid (AOAA; 250 microM), an inhibitor of pyridoxal phosphate-dependent enzymes such as C-S lyase, afforded protection, indicating that C-S lyase has a role in the bioactivation of these conjugates. In HPT cultures only DCVC caused significant time- and dose-dependent toxicity. Exposure to DCVC (500 microM) for 48 h decreased cell viability to 7% of control cell values, whereas co-incubation of DCVC (500 microM) with AOAA (250 microM) resulted in cell viability of 71%. Human cultures were also exposed to S-(1,2-dichlorovinyl)-glutathione (DCVG). DCVG was toxic to HPT cells, but the onset of toxicity was delayed compared with the corresponding cysteine conjugate. AOAA afforded almost complete protection from DCVG toxicity. Acivicin (250 microM), an inhibitor of gamma-glutamyl transferase (gamma-GT), partially protected against DCVG (500 microM)-induced toxicity at 48 h (5% viability and 53% viability in the absence and presence of acivicin, respectively). These results suggest that DCVG requires processing by gamma-GT prior to bioactivation by C-S lyase in HPT cells. The activity of C-S lyase, using TFEC as a substrate, and glutamine transaminase K (GTK) was measured in rat and human cells with time in culture. C-S lyase activity in RPT and HPT cells decreased to approximately 30% of fresh cell values by the time the cells reached confluence (120 h), whereas the decline in GTK activity was less marked (50% of the fresh cell values at confluence). Rat cells had threefold higher activity than human cells at each time point. This higher activity may partly explain the differences in toxicity between rat and human proximal tubular cells in culture.     

Hepatotoxicity following nevirapine-containing regimens in HIV-1-infected individuals.

To determine the incidence of hepatotoxicity and to investigate whether plasma concentrations of nevirapine, in addition to other risk factors, could predict hepatotoxicity during treatment with nevirapine-containing regimens, we conducted a retrospective analysis with data from 174 individuals infected with human immunodeficiency virus-1 (HIV-1). During regular visits to the clinic, blood samples were collected for the determination of nevirapine plasma concentrations and clinical chemistry parameters including liver enzymes (LEs) and total bilirubin (TBR). Severe hepatotoxicity was defined as a grade > or =3 elevation in at least one of the tested LEs or TBR levels while on therapy. Analysis of predictive factors was focused on increases in aspartate aminotransferase (ASAT) and/or alanine aminotransferase (ALAT) to grade > or =2. Grade > or =3 elevation developed with an incidence of 0.15 per patient year (PY); only 3.4% of the patients developed grade > or =3 values for ASAT and/or ALAT (incidence 0.03 per PY). We found that patients who use a protease inhibitor (PI) in a nevirapine-containing regimen and patients who have chronic hepatitis B (HBV) infection are at a higher risk for the development of increases in ASAT and/or ALAT to grade > or =2. In contrast, the plasma concentration of nevirapine does not appear to be a predictive factor in this study population.     

Trimetazidine ameliorates the hepatic injury associated with ischaemia-reperfusion in rats.

Ischaemia-reperfusion induces structural and functional damage to hepatocytes. The purpose of this study was to evaluate the protective effect of trimetazidine, an anti- ischaemic drug, in a rat liver model of ischaemia-reperfusion. Male Wistar rats were divided into groups pretreated with different doses of trimetazidine (1, 5, 10 or 20 mg kg-1 day-1) or saline for 7 days. Liver ischaemia was induced for 120 min and blood reflow was subsequently restored for 30, 60, 90 or 120 min. The activities of alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) as well as the bile flow and the liver ATP content were determined. Ischaemia-reperfusion induced major alterations of hepatic functions involving increases of ASAT and ALAT activities, a drop of ATP content and a sharp decrease in bile flow. Trimetazidine pretreatment reduced the liver injury. Indeed, it lowered the increase in ALAT and ASAT activities observed immediately after reperfusion and maintained higher concentrations of hepatic ATP. Simultaneously, bile flow was increased. These effects were dose-dependent and 5 mg kg-1 day-1 seemed to be the lowest effective dose. In this experimental model trimetazidine pretreatment reduced the liver damage induced by ischaemia-reperfusion. Our data suggest that trimetazidine may be a useful drug in liver surgery to prevent ischaemia-reperfusion injury.     

Biochemical changes induced in liver and serum of diplodiatoxin (Stenocarpella maydis) treated male and female rats

Present study was conducted to investigate the acute and sub-acute toxic effect of diplodiatoxin with special reference to biochemical membrane bound enzymes like aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and RBC acetylcholinesterase (AChE) in male and female rats. For acute study, rats were treated with a single oral dose of 5.7 mg/kg of diplodiatoxin, whereas for sub-acute study, the rats received 0.27 mg/kg/day for 21 days. Acute and sub-acute diplodiatoxin treatment caused loss in body weight and feed intake along with symptoms including irritation, dullness, tremors and convulsions. Diplodiatoxin caused a significant increase in serum ASAT and ALAT and a decrease in activity in the liver in both acute and sub-acute studies. This compound also significantly inhibited RBC AChE. Sexual dimorphism was observed when male rats were compared with female rats (p < 0.05). The enzyme alterations observed in the affected enzymes recovered to the normal levels by day 7 post treatment (withdrawal study) in both acute and sub-acute treated rats. A negative correlation was observed with regard to these enzymes when serum was compared with liver. These enzyme profiles show increases in serum with parallel decrease in liver, indicating necrosis of liver. These results suggest that diplodiatoxin has potential to affect hepatic end-points.     

The effects of moderate drinking and abstinence on serum and urinary beta-hexosaminidase levels

The effects of moderate alcohol intake on serum (SHEX)- and urinary beta-hexosaminidase (UHEX) were studied in ten healthy volunteers, who ingested 60 g of 100% ethanol daily for 10 days. The drinking period was preceded and followed by an abstinence period. Moderate drinking and abstinence were rapidly and significantly reflected on SHEX, while UHEX levels did not change significantly during the study. Gramma-glutamyl transpeptidase (GGT), aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) decreased during the first abstinence period (P less than 0.05), but stayed thereafter at a constant level. It is concluded that SHEX may better reflect recent alcohol consumption than UHEX, GGT, ASAT or ALAT.     

In Vivo and In Vitro Sevoflurane-Induced Lipid Peroxidation in Guinea-pig Liver Microsomes

Abstract: Sevoflurane is a recently introduced volatile inhalation anaesthetic and is already used commonly in Japan. We investigated the potential of sevoflurane to cause lipid peroxidation in vivo and in vitro. For the in vitro study, pentane formation in a mixture of guinea pig liver microsomes and sevoflurane in the presence of nicotinamide adenine dinucleotide phosphate (NADPH) was analyzed by gas chromatography. Under anaerobic conditions, pentane formed without sevoflurane, but sevoflurane potentiated this anaerobic pentane formation. Two antioxidant agents, vitamine E and glutathione, reduced the pentane formation induced by sevoflurane. In the in vivo study, 18 guinea pigs were exposed to air (control), 0.5% halothane, or 1.2% sevoflurane. The extent of lipid peroxidation and liver damage was investigated by measuring the level of thiobarbituric acid reactive products and serum transaminase (alanine-aminotransferase: ALAT and aspartate-aminotransferase: ASAT) activity 12 hr after exposure. Both halothane and sevoflurane significantly increased thiobarbituric acid-reactive products. The increase in thiobarbituric acid-reactive products seen with sevoflurane administration was half that seen with halothane. Sevoflurane increased the ALAT activity to the same extent as did halothane but did not increase the ASAT activity. We conclude that sevoflurane potentiates lipid peroxidation in guinea pig liver microsomes in vivo and in vitro. However, because the degree of liver damage as measured by transaminase activity was minimal and the mechanism of sevoflurane-induced lipid peroxidation is still unknown, we must be cautious in applying these results to humans.     

HEPATOPROTECTIVE EFFECT OF AMOORA ROHITUKA

Abstract

Antihepatotoxic activity of a resuspended residue of the alcohol extract of Amoora rohituka W & A. (Meliaceae) was studied in rats with hepatic injury induced by carbon tetrachloride. Carbon tetrachloride (1 ml/kg, i.p.) was administered twice a week for 3 weeks and an extract of A. rohituka (50 mg/kg/day) was given orally for the same period. The rats were sacrificed 24 h after the last CC1₄ challenge. Carbon tetrachloride induced elevations of alkaline phosphatase (ALP), glutamate pyruvate transaminase (CPT), alanine aminotransferase (ALAT), glutamate oxaloacetate transaminase (GOT), aspartate aminotransferase (ASAT) and lactate dehydrogenase (LDH) and total plasma bilirubin concentration as well as depression of total plasma cholesterol concentration were reduced significantly by the concurrent treatment of rats with A. rohituka suspension. Changes in the histological architecture of the liver produced by CC1₄ where also protected by the administration of A. rohituka suspension. These results indicate that A. rohituka suspension possesses hepatoprotective action.     

Inhibition of rat renal C-S lyase: assessment using kidney slice methodology

Renal C-S lyase enzymes are implicated in the biotransformation of xenobiotics into potentially toxic metabolites by a deviation from the normal pathways of glutathione conjugate processing. C-S lyase enzymes occur in gastro-intestinal bacteria, and in liver as well as in mammalian and avian kidney. The renal enzyme cleaves the carbon-sulphur bond in cysteine conjugates derived from halogenated olefins (e.g. tetrafluoroethene, trichloroethene, and hexachlorobutadiene). Substituted S-nitrophenyl conjugates, which are analogues of a substrate for the hepatic C-S lyase enzyme (S-2,4-dinitrophenyl-L-cysteine), are demonstrated to display significant inhibition of rat renal C-S lyase using kidney slice methodology. They are also shown to disrupt the tubular uptake of organic cations and anions.     

Formation of GSH-derivatives as a pathway for inactive intermediates in vinylidene chloride-treated rats

The two conjugates, S-[N-(2-hydroxyethyl)carbamoylmethyl]glutathione (GSAAE), and its corresponding mercapturic derivative N-acetyl-S-[N-(2-hydroxyethyl)carbamoylmethyl]cysteine (NCySAAE) were administered to fasted Sprague-Dawley rats as putative metabolites of vinylidene chloride (VDC). Methylthioacetylaminoethanol (MAAE) was identified in the urine of GSAAE- or NCySAAE-treated rats (0.5–2.0 mmol/kg i.p.), as well as in the urine of VDC-treated rats (0.5–2.0 mmol/kg p.o.). The effects of VDC, GSAAE and NCySAAE on the kidney and liver were also examined using aspartate aminotransferase (ASAT), N-acetyl-β-d-glucosaminidase (NAG) and β₂-microglobulin (β₂-m) as urinary parameters of nephrotoxicity, and glutamate dehydrogenase (GLDH), sorbitol dehydrogenase (SDH) and alanine aminotransferase (ALAT) as serum parameters of hepatotoxicity. Unlike treatment with VDC, treatment with both GSAAE and NCySAAE failed to cause kidney and liver toxicity. The results support the hypothesis that MAAE originates from the formation of GSAAE and further metabolization to NCySAAE, and that MAAE excretion does not reveal a pathway of reactive intermediates.     

Possible role of cysteine-S-conjugate β-lyase in species differences in cisplatin nephrotoxicity

To better understand species differences in cisplatin nephrotoxicity, we focused on renal cysteine-S-conjugate β-lyase (C-S lyase), which may play a crucial role in the metabolism of platinum (Pt)-cysteine conjugates. Aminooxyacetic acid hemihydrochloride (AOAA), an inhibitor of C-S lyase, reduced renal injuries due to cisplatin in rats, suggesting involvement of C-S lyase. On day 5 following a bolus cisplatin injection, three species showed in vivo nephrotoxic potentials in the order of rats > mice = rabbits (the highest to lowest), based on body surface. The levels of renal Pt residue at the nephrotoxic dose were in order of rabbits > rats > mice. Meanwhile, the activity of endogenous (basal) mitochondrial aspartate aminotransferase (AST), one of the C-S lyases, in the renal cortex of naive animals was rats > mice = rabbits. In a qualitative Western blot analysis, expression of mitochondrial C-S lyase in the kidney was observed at approximately 37 kDa in all five species used. In in vitro studies, the cytotoxicity of cisplatin was dependent on the expression level of C-S lyase mRNA in the respective renal cells. These results demonstrate that species differences in cisplatin nephrotoxicity are attributable to an interaction of renal Pt transition with C-S lyase activity.     

The effect of chlorpromazine and carbamazepine on diagnostically relevant liver enzymes

No interactions related to the analytical method were observed between chlorpromazine (1) or carbamazepine (2) and activities of alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), glutamate dehydrogenase (GLDH) or lactate dehydrogenase (LDH). With respect to its cytotoxic potential 1 in cultures of isolated rat hepatocytes increased markedly the release of enzymes into the culture medium, whereas the overall activities of the enzymes were not influenced. 2 in cultured hepatocytes caused no significant effects on the activities of the enzymes investigated. Besides the investigation of methodically related interactions in pooled human serum the methodic procedure including the use of cultures of isolated hepatocytes allows to study also pharmacologically and toxicologically related interactions between drugs and diagnostically relevant liver enzymes.     

Fumonisin B1-induced DNA damage in rat liver and spleen: effects of pretreatment with coenzyme Q10, L-carnitine, alpha-tocopherol and selenium.

Active oxygen radical species are reported to cause organ damage. This study was designed to determine whether oxidative stress contributed to the initiation or progression of hepatic and splenic cell DNA damage induced by fumonisin B1 (FB1) in rats. Another aim was to investigate the protective effects of the antioxidants coenzyme Q10 (CoQ10), L-carnitine, vitamin E (alpha-tocopherol) and selenium against DNA damage in the liver and spleen of rats treated with FB1. Fasted rats were injected intravenously with a single dose of fumonisin B1 at 1.55 mg kg-1 body wt. into the tail vein. Treatment with FB1 led to splenic and hepatic DNA fragmentation in 85% of the test animals. DNA fragmentation was investigated as a critical event in toxic cell death by testing total Ca2+ in liver. FB1 administration caused total Ca2+ in liver to increase within 4 h (204% of control). Measurement of liver enzyme activities showed an increase in aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT). FB1 also markedly decreased splenic and hepatic glutathione (GSH) levels. Pretreatment with CoQ10 (30 mg CoQ10 kg-1 diet) together with L-carnitine (2.8 mg carnitine kg-1 diet), alpha-tocopherol (30 IU vitamin E kg-1 diet) and selenium (1 mg selenium as sodium selenite kg-1 diet), decreased DNA damage and the activities of Ca2+, ASAT and ALAT in the liver. On the other hand, the level of GSH was slightly increased. The CoQ10 alone did not significantly protect against toxic cell death and glutathione depletion caused by FB1. Oxidative damage caused by FB1 may be one of the underlining mechanisms of FB1-induced cell injury and DNA damage.     

Fixed combination of candesartan with hydrochloro-thiazide in patients with severe primary hypertension

Objective:The new guidelines for treatment of hypertension by the JNC VII in 2003 permit the initial use of a combination therapy, if blood pressure has to be lowered more than 20/10 mmHg. The aim of this investigation was to document the efficacy and safety of a combination therapy with candesartan cilexetil and hydrochlorothiazide in severe hypertension.

Methods: 116 patients freshly diagnosed as having severe primary hypertension (Grade III) and untreated for this condition were enrolled. The study was performed without a placebo control group for ethical reasons. Thus, all patients were treated for 6 weeks with 16mg candesartan cilexetil plus 12.5mg hydrochlorothiazide daily after forced titration with 8 and 16mg candesartan cilexetil each for < 2 weeks. Sitting trough BP was measured always with the same

device in the morning after 15min at rest, and the median of three measurements was used for analysis. Safety parameters included alanyl aminotransferase (ALAT), aspartyl aminotransferase (ASAT), creatinine, urea, BUN and electrolytes.

Results: The mean reduction in systolic/diastolic BP at the end was 38.1/29.4mmHg. 90.1% of patients were considered to be responders, while 39.6% of patients treated became normotensive (< 140/< 90mmHg). No drug-related adverse events or changes in laboratory parameters were reported.

Conclusion: Although this was an open-label, single-group study, on the basis of efficacy and safety, the combination therapy appears to offer a promising treatment for patients with severe primary hypertension.     

Early biochemical and histological changes in rats exposed to a single injection of thioacetamide

Liver injury was induced by one subcutaneous administration of thioacetamide (200 mg/kg b.wt.) and studied 24 and 48 hrs later. Levels of aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) increased after 24 and 48 hrs. The lysosomal enzymes beta-hexosaminidase (beta-NAG) and beta-glucuronidase (beta-GLU) increased significantly after 24 hrs, while the level of beta-GLU returned to normal after 48 hrs, but the activity of beta-NAG remained significantly high even after 48 hrs. Histopathological examination showed necrotic hepatocytes around the central vein with infiltration of macrophages, neutrophils and eosinophils. The plasma zinc level decreased after 24 hrs and returned to normal after 48 hrs. Liver zinc content increased simultaneously at 24 hrs, returning to normal after 48 hrs. No alterations of plasma copper were observed after 24 and 48 hrs. Copper content of the liver increased significantly after 24 and 48 hrs. The present study thus shows that one dose of thioacetamide results in profound liver injury and supplementation of zinc prior to and simultaneously with thioacetamide normalized plasma zinc, increased liver zinc content and reduced the increase of beta-NAG, but did not influence the histological changes.     

Hepatoprotective Effect of the Total Alkaloid Fraction of Solanum pseudocapsicum Leaves

The total alkaloid fraction of the methanol extract of leaves of Solanum pseudocapsicum was tested for its hepatoprotective activity against CCl 4 induced toxicity in freshly isolated rat hepatocytes, HepG2 cells and animal models. The total alkaloid fraction was able to normalise the levels of aspartate amino transferase (ASAT), alanine aminotransferase (ALAT), alkaline phosphatase (ALP), triglycerides (TGL), total proteins, albumin, total bilirubin and direct bilirubin, which were altered due to CCl 4 intoxication in freshly isolated rat hepatocytes and also in animal models. The antihepatotoxic effect of the total alkaloid fraction was observed at very low concentrations (6–10µg/ml) and was found to be superior to that of the standard used. A dose dependent increase in the percentage viability was observed when CCl 4 exposed HepG2 cells were treated with different concentrations of the total alkaloid fraction. The highest percentage viability of HepG2 was observed at a concentration of 10µg/ml. Its in vivo hepatoprotective effect at 20 mg/kg body weight was comparable with that of the standard at 250mg/kg body weight. The total alkaloid fraction merits further investigation to identify the active principles responsible for the hepatoprotective properties. The results from the present investigation also indicate well correlation between the in vivo and in vitro studies.     

Glutathione- and cysteine-mediated cytotoxicity of allyl and benzyl isothiocyanate

Ally isothiocyanate has been reported to be a bladder carcinogen in male rats. On the other hand, benzyl isothiocyanate is an anti-carcinogen. These contradicting properties led us to investigate the cytotoxicity of these compounds in RL-4 rat hepatocytes. Since conjugation with glutathione plays an important role in the metabolism of these isothiocyanates, the glutathione and L-cysteine derivatives were also tested for cytotoxicity (electron microscopy, trypan blue exclusion, cell attachment, and inhibition of cell division). Both types of conjugates caused considerable toxicity: allyl isothiocyanate conjugates gave effects comparable to the parent compound, but benzyl isothiocyanate was more toxic than its conjugates. Addition of excess glutathione (greater than 4mM) to the free isothiocyanates as well as their conjugates abolished cytotoxicity up to the highest concentration tested (250 microM). Addition of excess L-cysteine (5 to 20 mM) lowered the effects but did not abolish them. The reaction of thiols with isothiocyanates was readily reversible: 15 min after dissolving the conjugates in buffer, pH 7.4, an equilibrium was established in which 9 to 15% of the conjugates was converted to free isothiocyanate. Two hours after addition of 1 mM of the L-cysteine conjugates to medium containing 5 mM glutathione, 80% of the total conjugates was present as the glutathione derivatives. The glutathione conjugates were similarly converted to L-cysteine conjugates. Glutathione conjugates are not able to enter the cell, thus their toxicity is presumably due to the release of free isothiocyanate, and in the presence of excess glutathione no toxicity was observed. L-cysteine derivatives are able to cross the cell membrane, thus excess L-cysteine diminishes cytotoxicity, since less free isothiocyanate is present outside the cells, but does not completely protect the cells. Glutathione and cysteine can be regarded as transporting agents for the isothiocyanates through the body. Initial detoxification can be followed by release of the reactive compound at some other site.     

An inhalation method for testing the toxicity of volatile compounds in small laboratory animals. A study on short-term and long-term toluene inhalation in rats

A coupola-shaped Plexiglass inhalation chamber (volume 190 I) with continuous infusion of toxicant and air flow was constructed for small laboratory animals. The method guarantees an even distribution of vapourized toxicant to 16 animals at the same time, and is convenient both in short-term and long-term experiments. As a volatile toxicant, toluene was used. The short-term and long-term effects of toluence on rats were studied using psychomotor tests, blood glucose, serum ALAT and ASAT values as well as hematocrit. Short-term exposure, but not long-term, impaired the performance in psychomotor tests, elevated blood glucose and serum ALAT and ASAT levels, and slightly increased hematocrit. Body weight decreased as compared to controls in short-term toluene exposure, but showed no difference in long-term treatment between toluene-and control groups at the end of exposure. The differences between the two exposures are probably due to the development of tolerance during long-term exposure either on receptor or metabolic level.     

Kynurenine aminotransferase activity in human liver: identity with human hepatic C-S lyase activity and a physiological role for this enzyme

The C-S lyase enzymes are responsible for the generation of mutagenic and cytotoxic metabolites via aberrant drug-metabolising pathways in mammalian tissues. We have examined human hepatic cytosolic, mitochondrial and microsomal fractions for evidence of C-S lyase activity. The cytosolic enzyme was purified using fast protein liquid chromatography over FFQ Sepharose, Mono P and Superose 12. An homogeneous protein (monitored by SDS-PAGE) was obtained following purification, and an 11-fold increase in C-S lyase specific activity was observed. The molecular weight of the enzyme was found to be 37 kDa in denaturing conditions, 82.3 kDa in non-denaturing conditions, and the C-S lyase activity was shown to co-purify with kynurenine aminotransferase activity when the transaminase activity of the enzyme was examined with kynurenine as the substrate.