[Effects of cholestasis on hepatotoxicity of acetaminophen in rats]

Acetaminophen high doses toxicity has been reported in clinical and experimental studies in relation with cytochrome P-450. (Acetaminophen metabolite). Thinking that biliary tract obstructions hould increases drugs toxicity because interferes toxic substances excretion or it modify the activity of P-450 we decided to study acetaminophen toxicity in rats with biliary tract obstruction. Male sprague Dawley rats were used (body weight 250-400 gr) in two groups: Group I control (6 rats) with choledoco bile duct ligated; two doses of saline solution 0.9% Intraperitoneal, 0.2 ml/100 gr. were administrated. Group II (Same surgical intervention) received two doses of acetaminophen (intraperitoneal) solution (400 mg/Kg). This group was divided in two (6 rats each), one of this was sacrificed at 48 h. and the other one at 120 h. after acetaminophen injection. Total, direct and indirect bilirubin, alkaline phosphatase, ALT and AST transaminases, hematology study, liver weight, histological studies of liver and kidney were performed in all rats. High incidence of liver necrosis ans significative transaminases increases were found in group II. Our results were discussed taking account that recent biliary tract obstruction increase acetaminophen toxicity, at a half doses reported in other studies. It is possible that mixed oxidation system activity of cytochrome P-450 was increased in our research.