Serum enzyme activities and hepatic triglyceride levels in acute and subacute acetaminophen-treated rats.

The dose- and time-related hepatotoxic effects of acetaminophen were investigated in rats using biochemical parameters as indices of hepatotoxicity supplemented by the histopathological examination of the livers. The acute or subacute (twice daily for 7 days) administration of 0.25 g/kg acetaminophen did not produce any noticeable hepatocellular damage. On the other hand, dose-dependent elevations in serum enzyme glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT) and sorbitol dehydrogenase (SDH) activities and hepatic triglyceride (TG) levels were observed following the administration of single doses of 0.5 and lg/kg acetaminophen. Maximal hepatic damage occurred 12-18 h after acute dosing, while the hepatic function returned to control levels by 48-72 h. In contrast with the acutely treated rats, the serum enzyme activities and the hepatic TG levels remained unchanged following 7-day treatment with 0.5 or 1 g/kg acetaminophen. Also, histopathologically the degree of acetaminophen-induced hepatic necrosis was found to be far less extensive in rats given 0.5 and 1 g/kg acetaminophen twice daily for up to one week, as compared with the animals sacrificed 18 h after administering single equivalent doses of this drug. The results suggest that the liver function is reversibly impaired following acetaminophen overdosage, and that the intensity of acetaminophen-induced hepatotoxicity becomes less severe after repeated exposure to this hepatotoxin.