Autoradiographic localization of the sites of uptake, cellular transport, and catabolism of low density lipoproteins in the liver of normal and estrogen-treated rats

摘要: Abstract The hepatic uptake and catabolism of low density lipoproteins are stimulated severalfold in rats treated with large amounts 17α-ethinylestradiol. To determine the sites within liver at which these processes occur, 125I-labeled human were injected intravenously into intact control estradiol-treated or added to perfusates their isolated livers. The livers fixed by perfusion processed for light electron microscopic autoradiography. Distribution autoradiographic silver grains was estimated qualitatively micrographs quantitatively micrographs. Many more seen from than rats, but processing labeled lipoprotein indistinguishable. Three minutes after intravenous injection livers, concentrated over microvillous surface parenchymal cells bordering space Disse. two half-distances endocytic pits. Only 5-15% endothelial Kupffer cells. Silver also observed vesicles beneath plasma membrane whose size shape suggested that they derived fusion vesicles. By 15 min, predominantly located structures like multivesicular bodies region GERL (Golgi complex-endoplasmic reticulum-lysosomes) near bile canaliculi. These packed small vesicle-like a few larger vesicles, latter possessing unit membrane. Between 30 when proteolysis is known begin, initially clear matrix body-like became dark frequently had dense tail-like appendage. At same time, began appear secondary lysosomes. other results indicate given estradiol follows pathway closely resembles well-defined “LDL receptor” cultured In be transported vesicles; fuse form acquire lysosomal enzymes converted lysosomes as degraded.