APPEARENCE OF GIANT PEROXISOMES IN MOUSE HEPATOCYTES TREATED WITH A HYPOLIPIDEMIC DRUG, SIMFIBRATE

An enlargement as well as a remarkable increase in number of peroxisomes was electron microscopically encountered in mouse hepatocytes treated for 7 days with 1, 3-propyl-bis (2-p-chlorophenoxy-2-methylpropanoate) (simfibrate, BCPMP), a hypolipidemic drug, that lowers serum chloesterol and triglycerids. Increase in number of peroxisomes was approximately 3 times of that in control cells. The general size of enlarged peroxisomes was 1.33×1.07μ, and approximately 2.5 times as compared with normal peroxisomes, 0.54×0.46μ, in control hepatocytes.The use of the term “giant peroxisomes (megaloperoxisomes)” is proposed in the present investigation.Giant peroxisomes had protein-riched matrix surrounded by a single membrane, and many of them contained a single nucleoid. Continuities or close associations between giant peroxisomes and the smooth or rough endoplasmic reticulum were frequently observed. Further detailed investigations on the origin of giant peroxisomes and relationship to pharmacological effect of BCPMP will be achieved.