MODULATION OF LIPID-METABOLISM AT RAT HEPATIC SUBCELLULAR SITES BY FEMALE SEX-HORMONES

The present studies examine the modulation of lipoprotein metabolism a t subcellular sites in the liver by female sex hormones. Subcutaneous injection of ethinyl estradiol (5 mg/kg) decreased both triacylglycero l (TG) lipase activity and neutral cholesteryl ester (CE) hydrolase ac tivity in hepatic endosomes while increasing lysosomal lipid hydrolysi s. These data suggest that estrogen may induce a shift in the site of intracellular lipid catabolism similar to that found in fasting animal s [1]. This work also shows that TG-lipase activity is increased in th e CURL and MVB endosomal fractions of ovariectomized rats compared to that found in the equivalent endosomal compartments of age-matched int act female controls. These observations are consistent with an inhibit ion of endosomal lipase by female sex hormones under physiologic condi tions.