title: Secretion of the newly synthesized cholesterol by rat hepatocytes in primary culture.
abstract: We used monolayer cultured rat hepatocytes as an experimental model to study the secretion of the newly synthesized cholesterol by the liver. Cellular cholesterol was labeled by exposing cultured hepatocytes to [14C]acetate prior to the study of secretion. Secretion of the newly synthesized cholesterol was measured by extracting cholesterol in the culture medium and assaying for the radioactivity of [14C]cholesterol. We found that: (a) cultured hepatocytes could secrete newly synthesized cholesterol in serum-free medium; (b) secreted [14C]cholesterol was bound to macromolecule(s) and the secretion rate was not affected by cycloheximide for up to 5 h; (c) serum added to the culture medium greatly enhanced hepatic cholesterol secretion; (d) serum high-density lipoproteins were most effective, lipoprotein-deficient serum (d greater than 1.21) less effective in stimulating cholesterol secretion, whereas low-density and very-low-density lipoproteins had little effect; (e) when the serum-free culture medium was fractionated by ultracentrifugation, a major portion of the secreted [14C]cholesterol was found in the high-density lipoprotein fraction; (f) part of the medium [14C]cholesterol also turned up in the high-density lipoprotein fraction when lipoprotein-deficient serum was added as the acceptor; (g) secreted [14C]cholesterol was found only in free form, although some of the cellular [14C]cholesterol was found as esters.
mesh_terms: D000818:Animals; D001769:Blood; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D003078:Colchicine / Q000494:pharmacology; D003470:Culture Media; D003513:Cycloheximide / Q000494:pharmacology; D003956:Dialysis; D005374:Filtration; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D008074:Lipoproteins / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D003470:Culture Media; D008074:Lipoproteins; D002784:Cholesterol; D003513:Cycloheximide; D006903:Hydroxymethylglutaryl CoA Reductases; D003078:Colchicine