Hypolipidemic activity and toxicity studies of a styrl-hexahydroindolinol, 34–250

34–250 evoked hypocholesterolemic activity in the rat (14, 25, 31, 52, 112 mg/kg, po), dog (10, 20, 40 mg/kg, po), and monkey (30 mg/kg, po). Serum triglycerides were lowered in the rat and dog but not in the monkey. 34–250 increased [¹⁴C]acetate incorporation into liver cholesterol, but incorporation of ¹⁴C-labeled acetate into serum cholesterol was decreased. Desmosterol or 7-dehydro-cholesterol did not accumulate in serum of the three species, suggesting that inhibition of cholesterol biosynthesis by 34–250 possibly does not occur at a late stage. Normal fecal bile acid excretion was observed in rats, suggesting that cholesterol catabolism probably was not enhanced by 34–250. Compound 34–250-induced hypocholesterolemia may result from inhibition of hepatic release of this sterol into blood. The reversible hepatic lipidosis observed in rats is also possibly related to decreased hepatic transport and/or secretion of triglycerides. 34–250 did not cause a proliferation of hepatic microbodies; the lack of an increase in this fatty acid oxidizing organelle suggests that it may also have had a role in increased hepatic lipidosis. In dogs, a high incidence of severe cataracts with an early onset was induced by 20 and 40 mg/kg, po of 34–250 despite the lack of desmosterol or 7-dehydro-cholesterol in serum. The absence of these late stage intermediates of cholesterol biosynthesis in the serum of a test species does not preclude the occurrence of ocular toxicity.