Isopropanol and acetone potentiation of carbon tetrachloride-induced hepatotoxicity: single versus repetitive pretreatments in rats

Acetone Ingestion Mimics a Fasting State to Improve Glucose Tolerance in a Mouse Model of Gestational Hyperglycemia

Gestational diabetes mellitus results, in part, from a sub-optimal β-cell mass (BCM) during pregnancy. Artemisinins were reported to increase BCM in models of diabetes by α- to β-cell conversion leading to enhanced glucose tolerance. We used a mouse model of gestational glucose intolerance to compare the effects of an artemisinin (artesunate) on glycemia of pregnant mice with vehicle treatment (acetone) or no treatment. Animals were treated daily from gestational days (GD) 0.5 to 6.5. An intraperitoneal glucose tolerance test was performed prior to euthanasia at GD18.5 or post-partum. Glucose tolerance was significantly improved in both pregnant and non-pregnant mice with both artesunate and vehicle-alone treatment, suggesting the outcome was primarily due to the acetone vehicle. In non-pregnant, acetone-treated animals, improved glucose tolerance was associated with a higher BCM and a significant increase in bihormonal insulin and glucagon-containing pancreatic islet cells, suggesting α- to β-cell conversion. BCM did not differ with treatment during pregnancy or post-partum. However, placental weight was higher in acetone-treated animals and was associated with an upregulation of apelinergic genes. Acetone-treated animals had reduced weight gain during treatment despite comparable food consumption to non-treated mice, suggesting transient effects on nutrient uptake. The mean duodenal and ileum villus height was reduced following exposure to acetone. We conclude that acetone treatment may mimic transient fasting, resulting in a subsequent improvement in glucose tolerance during pregnancy.

Technical note: Residues of gaseous air pollutants in rabbit (Oryctolagus cuniculus) tissues

The modern consumer is concerned not only for meat quality, but also about animal welfare and the environment. Studies were conducted to determine the concentration of gaseous residues in the tissues of rabbits. For this purpose, gaseous air pollutants were measured at the height of rabbit cages. Immediately after slaughter, samples were taken for analysis to determine the level of residual pollutants in the tissues (blood, perirenal fat and lung). Headspace gas chromatography was performed on the tissue samples to test for volatile toxic substances. Gas residues of 11 compounds were determined in the samples of blood, perirenal fat and lungs. The same chemicals were present in the air of the farm and the animal tissues, which may indicate their capacity for bioaccumulation. We recommend that the results should be used to develop guidelines regarding the welfare of meat rabbits and requirements for laboratory rabbits.

Anti-atherogenic and anti-ischemic potentials of Croton membranaceus observed during sub-chronic toxicity studies

BACKGROUND

Croton membranaceus (CM) is used for benign prostate hyperplasia treatment.

OBJECTIVE

Sub-chronic toxicity studies are non-existent and provided the basis for this study.

MATERIALS AND METHODS

90 days oral administration of a low dose (LD) (30 mg/kg b. wt.), medium dose (MD) (150 mg/kg b. wt.), and high dose (HD) (300 mg/kg b. wt.) CM aqueous root extract to 3 groups (n=6 each) of male Sprague-Dawley rats, alongside a control group, was undertaken. Urinalysis, hepato-renal function tests, lipid profile, cardiac enzymes, and routine hematology tests were performed.

RESULTS

Triglyceride levels (C=1.05±0.19, LD=0.64±0.08, MD=0.55±0.04, HD=0.50±0.02 mmol/L) were significantly reduced (P<0.05). Very low density lipoprotein (C=0.48±0.09, LD=0.29±0.04, MD=0.25±0.02, HD=0.23±0.01 mmol/L) decreased significantly (P<0.05). Cardiac enzymes-creatinine kinase (C=568±172, LD=315±79, MD=441±209, HD=286±81 IU/L) decreased markedly (P<0.05) alongside lactate dehydrogenase (C=2675±875, LD=1667±1229, MD=1186±442, HD=855±239 IU/L) (P<0.05).

CONCLUSION

C. membranaceus aqueous root extract is non-toxic but demonstrates anti-atherogenic and anti-ischemic potentials.

Acetone in drinking water does not modulate humoral immunity in mice as measured by the antibody, plaque-forming cell assay

It has been reported that the repeated topical, nonoccluded application of acetone may modulate antibody production in mice, thus producing humoral immunosuppression. However, the evaporative loss expected following nonoccluded dermal application of acetone makes the systemic effect seem unlikely. This study was designed to investigate the immunotoxicity potential of acetone in mice following a more direct systemic route of dosing via drinking water for 28 days. CD-1 male mice consumed average daily acetone doses of 121, 621 or 1144 mg/kg/day. The antibody, plaque-forming cell (AFC) assay was performed to measure the T cell-dependent, anti-sheep red blood cell immunoglobulin M (IgM) response, and hematology and thymus weights were evaluated to provide additional insight into the potential effects to the immune system. Body weights, white blood cell (WBC), numbers, red blood cell (RBC) counts, and hemoglobin and hematocrit levels showed no treatment-related effects at any dose of acetone. Eosinophil percentages were variable but also showed no dose-related trends. Spleen and thymus weights were not statistically different from controls and there were no effects on spleen cellularity or AFC response as a result of acetone administration. The AFC responses ranged from 1088 to 1401 AFCs/10(6) splenocytes and were not statistically different from controls (1277 AFCs/10(6) cells). Mice treated with cyclophosphamide (20 mg/kg) on days 25 to 28 demonstrated a 94% reduction in AFC/10(6) cells. Thus, the direct systemic administration of acetone did not produce evidence for immunotoxicity in CD-1 mice and the no observed adverse effect level (NOAEL) in this study was determined to be 1144 mg/kg/day.

Toxicokinetics of organic solvents: a review of modifying factors

This article reviews, with an emphasis on human experimental data, factors known or suspected to cause changes in the toxicokinetics of organic solvents. Such changes in the toxicokinetic pattern alters the relation between external exposure and target dose and thus may explain some of the observed individual variability in susceptibility to toxic effects. Factors shown to modify the uptake, distribution, biotransformation, or excretion of solvent include physical activity (work load), body composition, age, sex, genetic polymorphism of the biotransformation, ethnicity, diet, smoking, drug treatment, and coexposure to ethanol and other solvents. A better understanding of modifying factors is needed for several reasons. First, it may help in identifying important potential confounders and eliminating negligible ones. Second, the risk assessment process may be improved if different sources of variability between external exposures and target doses can be quantitatively assessed. Third, biological exposure monitoring may be also improved for the same reason.

Stimulatory effect of anesthetics on dechlorination of carbon tetrachloride in guinea-pig liver microsomes

Effects of the anesthetics isoflurane, enflurane, halothane and sevoflurane on the dechlorination of carbon tetrachloride to produce chloroform were investigated using guinea pig liver microsomes. Under anaerobic conditions, chloroform is produced from carbon tetrachloride by the microsomes in the presence of NADPH, and chloroform production from 86 microM carbon tetrachloride was enhanced to 146%, 133%, 123% and 115% by the addition of isoflurane, enflurane, halothane and sevoflurane, respectively. The half-life of oxidized cytochrome P450 which remained during the reduction by the addition of NADPH was shortened to 51%, 54%, 60% and 80% by isoflurane, enflurane, halothane and sevoflurane, respectively, without alteration of NADPH-cytochrome c reductase activity. These anesthetics hastened the onset of the 445 nm absorption band formation which was shown by microsomes with carbon tetrachloride in the presence of NADPH under anaerobic conditions. These results indicate that the anesthetics isoflurane, enflurane, sevoflurane and halothane stimulate the reduction of cytochrome P450 results in the acceleration of the carbon tetrachloride dechlorination. These results may have implications for other type II drugs that are administered during anesthesia.

Ketone potentiation of haloalkane-induced hepato- and nephrotoxicity. I. Dose-response relationships

Carbon tetrachloride (CCl4) induced hepatotoxicity and chloroform (CHCl3) induced nephrotoxicity were evaluated in male Sprague-Dawley rats pretreated with acetone (A), methyl ethyl ketone (MEK), and methyl isobutyl ketone (MiBK). Dose-response relationships for A, MEK, and MiBK potentiation of CCl4-induced hepatotoxicity and CHCl3-induced nephrotoxicity were compared. A, MEK, and MiBK pretreatment at a dosage of 6.8 mmol/kg, given daily for 3 d, markedly potentiated CCl4-induced liver toxicity as indicated by a decrease in the CCl4 ED50 to 3.4, 4.6, and 1.8 mmol/kg, respectively, compared to vehicle-pretreated rats (17.1 mmol/kg). Similarly, pretreatment with these ketones (13.6 mmol/kg) potentiated CHCl3 kidney toxicity but to a lesser degree; CHCl3 ED50 values for vehicle-, A-, MEK-, and MiBK-pretreated rats were 3.4, 1.6, 2.1, and 2.2 mmol/kg, respectively. Our results indicate a potency ranking profile for the potentiation of CCl4 hepatotoxicity of MiBK > A > MEK and of A > MEK > or = MiBK for CHCl3 nephrotoxicity. These dissimilar ranking profiles could be due to differences in mechanisms of action for the two target sites.

Two-generation reproduction toxicity study with isopropanol in rats

A two-generation reproduction toxicity study was conducted in rats with isopropanol. Thirty rats of each sex per group (P1) were dosed once daily by oral gavage with 0, 100, 500 or 1000 mg isopropanol kg-1 for at least 10 weeks prior to mating. Parental animals were mated within groups for up to 3 weeks. Parental females were dosed during mating, gestation and lactation; parental males were dosed during mating through delivery of their last litter sired. The P2 adults were selected from the F1 litters and were dosed for 10-13 weeks before mating to produce a single litter. Findings in the parental animals included increased lactation body weight gain in the mid- and high-dose females, increased liver and kidney weights in the mid- and high-dose groups of both sexes and centrilobular hepatocyte hypertrophy in some P2 males. There was also accumulation of hyaline droplets and other microscopic findings in the kidneys from the mid- and high-dose P1 males and from all treated groups of the P2 males. Increased mortality was observed in the high-dose F1 offspring during the early postnatal period, although no other clinical signs of toxicity were observed in the offspring of either generation. In addition, offspring body weight was reduced during the early postnatal period in the high-dose F1 males and in the high-dose F2 pups of both sexes. Eighteen out of 70 F1 weanlings in the 1000 mg kg-1 group died or were euthanized prior to P2 selection. No treatment-related post-mortem findings were observed in the offspring from either generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Post-translational reduction of cytochrome P450IIE by CCl4, its substrate

The molecular mechanism of cytochrome P450IIE reduction by CCl4 was reexamined by measuring its enzyme activity, immunoreactive protein contents, and mRNA levels. Aniline hydroxylase and the amounts of immunoreactive P450IIE were rapidly decreased in a time-dependent manner after a single dose of CCl4. No changes were observed in the amounts of immunoreactive P450IIC and P450IA despite significant decreases decrease in their catalytic activities. However, the decreases in P450IIE enzyme activity and immunoreactive protein by CCl4 were not accompanied by a decline in its mRNA level. The data thus suggested a post-translational reduction of P450IIE by CCl4, probably due to specific destruction of the P450IIE protein by its own substrate rather than heme moiety.

Effects of acetone administration on cytochrome P-450-dependent monooxygenases in hamster liver, kidney, and lung

The effects of acetone on liver, kidney, and lung monooxygenases were studied using hamsters administered 8% acetone in drinking water. Binding of aniline to liver microsomes induced a type II difference spectrum, and the spectral binding was enhanced in hamsters pretreated with acetone. Administration of acetone caused significant increases of cytochrome P-450 and cytochrome b5 contents in liver microsomes. The increases of the hemeproteins were associated with induction of monooxygenase activities toward test substrates, aniline, N-nitrosodimethylamine, benzphetamine, benzo(a)pyrene, and 7-ethoxycoumarin. In the kidneys, acetone administration increased microsomal contents of the hemeprotein and monooxygenase activities toward aniline. N-nitrosodimethylamine, and 7-ethoxycoumarin, but not benzphetamine or benzo(a)pyrene. In the lungs, acetone pretreatment increased aniline hydroxylase activity without affecting the levels of N-nitrosodimethylamine demethylase, cytochromes P-450 and b5. In marked contrast to the inductive effects in the liver, acetone administration markedly decreased lung microsomal benzo(a)pyrene hydroxylase and 7-ethoxycoumarin O-deethylase activities. Gel electrophoresis of liver and kidney microsomes from control and acetone-treated hamsters revealed that acetone treatment enhanced the intensity of a protein band(s) in the cytochrome P-450 molecular weight region. Immunoblotting of the microsomal proteins showed that the protein band induced by acetone in hamster liver, kidney and lung was cross-reactive with antibody raised against ethanol-inducible human liver cytochrome P-450. These results demonstrate that acetone has the ability to uniformly induce a specific form of cytochrome P-450, designated as IIE1, and to cause differential changes of monooxygenase activities in the hamster tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acetone and methyl n-butyl ketone on hepatic mixed-function oxidase

The administration of ketones potentiates CCl4 hepatotoxicity; however, the potencies of the ketones differ. The aim of the present study was to assess potential differences between acetone and methyl n-butyl ketone (MnBK) on cytochrome P-450. The effects of single and repetitive doses of acetone and MnBK were determined in male rats by estimating the rate of metabolite formation of three substrates and the hepatic content of cytochrome P-450. A single treatment with acetone (13.5 mmol/kg or greater) enhanced the oxidation of aniline and 7-ethoxycoumarin, whereas repetitive treatments also increased aminopyrine demethylation and cytochrome P-450 content. Single and repetitive treatments of MnBK (15 mmol/kg) augmented the oxidation of all three substrates and increased cytochrome P-450 content. The effects of the ketones on cytochrome P-450 isozymes were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Acetone and MnBK increased the 52.1 and 54.1 kD forms and, in addition, MnBK tended to increase the 50.6 kD species. The data indicate that ketones differ in the type of isozymes induced and in the degree of induction. The higher potency of MnBK, compared to acetone, is probably associated with the fact that MnBK affects a greater number of isozymes than acetone.

Potentiation of CCl4-induced liver injury by ketonic and ketogenic compounds: role of the CCl4 dose

Potentiation of haloalkane hepatotoxicity by ketones and ketogenic agents is a well-known phenomenon. The importance of the CCl4 dosage in these combinations, however, has not been explored. Its influence was investigated in male Sprague-Dawley rats. Dose-effect curves for potentiation were generated using 1,3-butanediol, methyl n-butyl ketone or methyl isobutyl ketone as potentiation agents. Animals were orally treated with these compounds prior to a challenge of CCl4 (0 to 0.5 ml/kg, ip). Liver injury was assessed by monitoring plasma ALT activity and bilirubin concentrations after CCl4 treatment. The minimal effective dosage (MED) for each potentiator was used as the criterion of comparison for each combination. The MED values were determined from the plasma ALT data. Results showed that when the CCl4 dosage was increased from 0.01 to 0.10 ml/kg, the MED of each potentiator decreased 10-fold. For a given potentiator, the product of the CCl4 dosage (H, "hepatotoxicant") by the corresponding MED value (P, "potentiator") remained the same in this range of CCL4 dosages. The severity of the liver injury was similar. These findings suggest that a given level of liver injury induced by a ketone/haloalkane combination could be evaluated on the basis of the [P X H] product.

Microsomal metabolism of acetonitrile to cyanide. Effects of acetone and other compounds

Oral acetone exposure delays and potentiates acetonitrile toxicity in rats. Results of previous pharmacokinetic studies suggested that acetone exerted a biphasic effect on the metabolism of acetonitrile to cyanide; the presence of acetone in vivo appeared to inhibit the metabolism of acetonitrile to cyanide, whereas the disappearance of acetone from serum was followed by stimulation of acetonitrile metabolism. The current experiments were designed to characterize further the metabolism of acetonitrile to cyanide and the effects of acetone and other compounds upon this metabolism. Liver microsomes were isolated and pooled 24 hr after oral pretreatment of female Sprague-Dawley rats (180-250 g) with acetone (1960 mg/kg) or water. Microsomal metabolism of acetonitrile to cyanide was found to be oxygen and NADPH dependent, and heat-inactivated tissue was unable to catalyze the reaction. NADH antagonized the NADPH-dependent metabolism of acetonitrile. The metabolism of acetonitrile to cyanide was linear with protein concentrations of 0-8 mg per incubation. Following a characteristic lag period of 10 min, the reaction was linear from 15 to 30 min. This metabolism was inhibited by carbon monoxide, metyrapone and SKF 525-A. Acetone pretreatment (-24 hr) in vivo increased the apparent Vmax for acetonitrile metabolism without affecting the apparent Km. When added in vitro, acetone competitively inhibited the metabolism of acetonitrile, with a KI of 0.41 mM. Dimethyl sulfoxide (KI = 0.51 mM) and ethanol (KI = 0.11 mM) were also competitive inhibitors of acetonitrile metabolism, and aniline HCl (KI = 4.77 microM) appeared to be a mixed inhibitor. These data are consistent with the hypothesis that the metabolism of acetonitrile to cyanide is mediated by a specific acetone-inducible isozyme of cytochrome P-450.

Correlation between acetone-potentiated CCl4-induced liver injury and blood concentrations after inhalation or oral administration

In studies of acetone-potentiated liver injury induced by haloalkanes, acetone is usually given by gavage, whereas industrial exposure to acetone normally occurs by inhalation. It was of interest to verify if the route of administration influences the potentiation. Male Sprague-Dawley rats were exposed for 4 hr to acetone vapors or treated orally with acetone; the minimal effective dose (MED) levels for potentiating CCl4-induced liver injury were estimated to be 2500 ppm and 0.25 ml/kg, respectively. Groups were treated with acetone using 0.4, 1, 2, 4, or 6 times the MED. Half of each group was killed at various time intervals after treatment for blood acetone measurements by gas chromatography; the other half was challenged with CCl4 (0.1 ml/kg, ip) 18 hr after acetone, and killed 24 hr later. Plasma alanine aminotransferase (ALT) activity and bilirubin concentrations were measured. Inhalation and oral administration of acetone both potentiated CCl4 toxicity. Rats exposed repetitively to acetone vapors (10 daily exposures) and subsequently challenged with CCl4 exhibited liver toxicity that was not significantly different from that of rats subjected to a single exposure. Correlations between ALT activities and maximal blood acetone concentrations were found to be linear (positive) and significant for both routes. For a given blood acetone concentration, however, toxicity was least severe following acetone exposure by inhalation. When the concept of threshold concentrations was applied to the data, the severity of the toxic response was dependent on the blood acetone concentration above the threshold, irrespective of the route of administration.

Uptake, distribution, metabolism, and elimination of styrene in man. A comparison between single exposure and co-exposure with acetone

Six male subjects were exposed for two hours during light physical exercise to 2.81 mmol/m3 (293 mg/m3) of styrene on one occasion and to a mixture of 2.89 mmol/m3 (301 mg/m3) of styrene and 21.3 mmol/m3 (1240 mg/m3) of acetone on another (combination study). About 68% of the dose (somewhat more than 4 mmol) of styrene was taken up. The arterial blood concentration of styrene reached a relatively stable level after about 75 minutes of exposure of about 18 and 20 mumol/l after the single and combined exposure, respectively. Calculated values of mean blood clearance were 1.9 l/min in the styrene study and 1.6 l/min in the combination study; the half life of styrene in blood was about 40 minutes in both studies. The concentration of non-conjugated styrene glycol increased linearly during exposure and reached about 3 mumol/l at the end of exposure and was eliminated with a half life of about 70 minutes. Styrene-7,8-oxide was detected and quantified in the blood in a complementary study. The half lives for the excretion of mandelic and phenylglyoxylic acid in the urine were about four and nine hours, respectively, in both studies.

Potentiation of the hepatotoxicity of N-nitrosodimethylamine by fasting, diabetes, acetone, and isopropanol

Previous studies indicate that pretreatment with acetone or isopropanol, fasting, and streptozotocin-induced diabetes enhance hepatic microsomal nitroso-dimethylamine (NDMA) demethylase in rats. This study demonstrates that these same treatments also potentiate the hepatotoxicity of NDMA as indicated by plasma glutamic pyruvate transaminase (GPT) levels and histologic data. Pretreatment with acetone or isopropanol (2.5 ml/kg) and 2 days of fasting caused a 2-fold potentiation of NDMA-induced plasma GPT elevation, whereas streptozotocin-induced diabetes caused a 4.6-fold potentiation. The centrilobular necrosis produced by NDMA was more severe after pretreatment with the inducers. NDMA treatment also decreased hepatic microsomal demethylase activity. These results lend support to the concept that a NDMA demethylase is responsible for the activation of NDMA in vivo to a toxic intermediate, and induction of this enzyme activity potentiates NDMA hepatotoxicity.

Studies on the mechanisms of induction of N-nitrosodimethylamine demethylase by fasting, acetone, and ethanol

Previous work has shown that induction of a high-affinity NADPH-dependent nitrosodimethylamine demethylase (NDMAd) in liver microsomes occurs in rats due to fasting, ethanol consumption, and streptozotocin-induced diabetes. Several lines of observations suggest that this is due to the induction of specific cytochrome P-450 isozymes. Induction of P-450 species by ethanol has also been observed by other investigators. Since each of the above altered metabolic states has in common elevated levels of ketone bodies, the possible role of acetone, a known inducer of NDMAd, in the induction of the demethylase activity was investigated. Levels of endogenous acetone in fasted rats correlated (r = 0.72) with a three- to fourfold increase in NDMAd activity. However, a dose-response experiment showed endogenous levels of acetone to be capable of causing at most 40% of the induction in fasted rats. This suggests that other ketone bodies or factors may have contributed to the induction. The induction of NDMAd by ethanol was enhanced by alcohol dehydrogenase inhibitors pyrazole and acetaldehyde oxime, suggesting that ethanol, rather than its metabolites, was responsible for the induction.

Isopropanol enhancement of cytochrome P-450-dependent monooxygenase activities and its effects on carbon tetrachloride intoxication

Acute or chronic treatment of rats with isopropanol caused a significant increase in hepatic cytochrome P-450 content and a two- to threefold increase in aniline hydroxylase and 7-ethoxycoumarin O-deethylase activities, but no significant change in ethylmorphine N-demethylase or benzo(a)pyrene hydroxylase activity. In rats treated with isopropanol and challenged with CCl4, liver toxicity of CCl4 was characteristically potentiated, as assessed by elevation of serum glutamic-pyruvic transaminase (SGPT) levels. Isopropanol pretreatment also potentiated CCl4-induced damage to the hepatic monooxygenase system. In addition to a decrease in cytochrome P-450, rats treated with isopropanol and challenged with CCl4 showed a nonspecific decrease not only in aniline hydroxylase and 7-ethoxycoumarin O-deethylase activities, but also in ethylmorphine N-demethylase, benzo(a)pyrene hydroxylase, and NADPH-cytochrome c reductase activities. These results were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of solubilized microsomes. The electrophoretic results showed that isopropanol pretreatment markedly potentiated the CCl4-caused destruction of cytochrome P-450 hemeproteins. The data strongly suggest that isopropanol increases one or more forms of cytochrome P-450 which selectively enhance the metabolism of CCl4 to an active metabolite. This active metabolite then causes a nonselective damage to the microsomal mixed-function oxidase system.

Relationship between the carbon skeleton length of ketonic solvents and potentiation of chloroform-induced hepatotoxicity in rats

Previous studies have suggested that ketonic solvents potentiate the hepatotoxic action of CHCl3 in rats. In addition, the relative potentiating capacity of the ketones appeared to be related to the length of their carbon skeleton. To test this hypothesis CHCl3-induced liver injury was evaluated in male Sprague-Dawley rats pretreated (15 mmol/kg, p.o.) with acetone (Ac), 2-butanone (Bu), 2-pentanone (Pn), 2-hexanone (Hx) or 2-heptanone (Hp). After 18 h, a challenging dose of CHCl3, (0.50 or 0.75 ml/kg, i.p.) was given. Liver damage was evaluated 24 h after CHCl3 administration by determining elevations in plasma GPT and OCT activity. Neither Ac, Bu, Pn, Hx, Hp or the CHCl3 challenging dosages produced marked liver injury when given alone. However, each of the ketones potentiated CHCl3-induced liver damage. The severity of the potentiated hepatotoxic response was significantly (positively) correlated with the ketone carbon chain length. These observations suggest that carbon skeleton length may play a role in determining the relative potentiating capacity of ketonic solvents.