title: The intracellular distribution of high density lipoproteins taken up by isolated rat hepatocytes.
abstract: The subcellular distribution of 125I-labelled HDL taken up by rat hepatocytes in vivo and in vitro has been studied with subcellular fractionation techniques: differential centrifugation and isopycnic centrifugation in sucrose gradients. 125I-labelled HDL bind to plasma membranes both in vivo and in vitro and part of the membrane-bound 125I-labelled HDL can be dissociated by the addition of unlabelled HDL. The hepatocytes also internalize 125I-labelled HDL. The 125I-labelled HDL accumulate, however, at different intracellular sites in the in vivo and in vitro situation. The subcellular distribution pattern of 125I-labelled HDL taken up by the cells in vivo is similar to that of the lysosomal marker enzyme acid phosphatase. Peak activity was found at a density of 1.20 g/ml. In vitro 125I-labelled HDL accumulate in an organelle with a medium density of about 1.13 g/ml. This distribution was similar to that of the plasma membrane marker 5'-nucleotidase. The subcellular distribution of radioactivity taken up in vivo was changed to lower density by incubating the cells with chloroquine, a drug known to render the lysosomes more boyant. Chloroquine had no effect on the distribution of 125I-labelled HDL taken up by hepatocytes in vitro.
mesh_terms: D015720:5'-Nucleotidase; D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D002500:Centrifugation, Isopycnic; D002738:Chloroquine / Q000494:pharmacology; D004705:Endocytosis; D008075:Lipoproteins, HDL / Q000302:isolation & purification* / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D009708:Nucleotidases / Q000378:metabolism; D051381:Rats
chemical_list: D008075:Lipoproteins, HDL; D002738:Chloroquine; D009708:Nucleotidases; D000135:Acid Phosphatase; D015720:5'-Nucleotidase