Hepatic injury induces contrasting response in liver and kidney to chemicals that are metabolically activated: role of male sex hormone.

Injury to liver, resulting in loss of its normal physiological/biochemical functions, may adversely affect a secondary organ. We examined the response of the liver and kidney to chemical substances that require metabolic activation for their toxicities in mice with a preceding liver injury. Carbon tetrachloride treatment 24 h prior to a challenging dose of carbon tetrachloride or acetaminophen decreased the resulting hepatotoxicity both in male and female mice as determined by histopathological examination and increases in serum enzyme activities. In contrast, the renal toxicity of the challenging toxicants was elevated markedly in male, but not in female mice. Partial hepatectomy also induced similar changes in the hepatotoxicity and nephrotoxicity of a challenging toxicant, suggesting that the contrasting response of male liver and kidney was associated with the reduction of the hepatic metabolizing capacity. Carbon tetrachloride pretreatment or partial hepatectomy decreased the hepatic xenobiotic-metabolizing enzyme activities in both sexes but elevated the renal p-nitrophenol hydroxylase, p-nitroanisole O-demethylase and aminopyrine N-demethylase activities significantly only in male mice. Increases in Cyp2e1 and Cyp2b expression were also evident in male kidney. Castration of males or testosterone administration to females diminished the sex-related differences in the renal response to an acute liver injury. The results indicate that reduction of the hepatic metabolizing capacity induced by liver injury may render secondary target organs susceptible to chemical substances activated in these organs. This effect may be sex-specific. It is also suggested that an integrated approach should be taken for proper assessment of chemical hazards.

Contrasting changes in phase I and phase II metabolism of acetaminophen in male mice pretreated with carbon tetrachloride.

Effect of carbon tetrachloride (CCl(4)) pretreatment on the biotransformation and elimination of acetaminophen were examined in male mice. A 24 hr initial dose of CCl(4) (0.05 ml/kg, intraperitioneally) reduced the induction of hepatotoxicity resulting from acetaminophen treatment (350 mg/kg, intraperitoneally) as determined by changes in serum alanine and aspartate aminotransferase, and sorbitol dehydrogenase activities. Acetaminophen and the major metabolites in plasma were monitored for 12 hr following acetaminophen treatment. CCl(4) pretreatment decreased the plasma concentrations of acetaminophen-cysteine and acetaminophen-mercapturate, but acetaminophen-glucuronide and acetaminophen-sulfate were increased significantly. The elimination of the parent drug from plasma was not affected by CCl(4). In urine collected for 24 hr, the concentrations of acetaminophen-sulfate and acetaminophen-glucuronide were increased by 84% and 33%, respectively, whilst acetaminophen-cysteine and acetaminophen-mercapturate were reduced to approximately one third of control. Expression of cytochrome P450 (CYP) isozymes was determined using antibodies of 2E1 and 1A2 as probes. CYP2E1 and 1A2 expressions were decreased significantly by CCl(4). Likewise, CCl(4) treatment reduced the microsomal p-nitrophenol hydroxylase and p-nitroanisole O-demethylase activities to less than one third of control. The results indicate that, although CCl(4) reduces the generation of thioether conjugates of acetaminophen by decreasing the CYP activities, inhibition of the oxidative metabolism of acetaminophen is counterbalanced by the enhancement of conjugate formation via the glucuronide and sulfate pathways, resulting in elimination of the drug at a rate equivalent to that in normal mice. It is suggested that liver injury in patients may not warrant a mandatory reduction of drug doses extensively inactivated via phase II reactions.