MICROBODIES IN EXPERIMENTALLY ALTERED CELLS VII. CPIB-induced Hepatic Microbody Proliferation in the Absence of Significant Catalase Synthesis

Previous studies (1-3) demonstrated a significant increase in number of microbodies (peroxisomes) and concomitant elevation in catalase activity in male rat liver following administration of ethyl-o, p-chlorophenoxyisobutyrate (clofibrate, CPIB), a hypolipidemic drug that lowers serum cholesterol and triglycerides in man (4) and in experimental animals (5, 6) . Neither the significance of microbody proliferation induced by CPIB nor the nature of controlling mechanism(s) involved is known, although a possible relation of microbodies to lipid metabolism has been suggested (7) . That proliferation of hepatic microbodies in rats is independent of hypolipidemia fol lowing CPIB treatment, however, has been shown in studies in which thyroidectomy abolished the