The effects of misoprostol (cytotec, SC29333) on circulating lipoproteins and liver microsomal enzyme activity were studied. Misoprostol increased serum levels of high density lipoprotein-cholesterol and decreased total cholesterol and triglycerides. The high density lipoprotein-cholesterol/total cholesterol ratio increased by 54.8%. In parallel, misoprostol significantly altered enzyme hepatic activity. Liver microsomal cytochromes P450 and b5 were significantly increased in correlation with enhanced liver aminopyrine N-demethylase and antipyrine hydroxylase activities, suggesting a liver induction effect of misoprostol. Other observations such as increased liver weight and glycogen and increased plasma albumin and glucose in rats receiving misoprostol support this evidence.