title: Time course of release into the medium of newly synthesized proteins by cultured aortic endothelial cells. Role of serum in preventing proteolytic degradation.
abstract: Endothelial cells from pig aortas were labeled with 35S-methionine, and the soluble proteins that were released into the culture medium were examined by SDS-PAGE. Proteins were collected during labeling, and during the intervals 0 to 3, 3 to 6, 6 to 12, and 12 to 24 hours of chase after a 1-hour labeling period, and during the intervals 0 to 12, 12 to 24, and 24 to 48 hours of chase after a 24-hour labeling period. Release of radiolabeled soluble protein from cells into the medium continued over the longest time periods examined. If the cells were labeled for 1 hour, characteristic patterns of proteins appeared in the medium during the labeling period, early (0- to 3-hour postlabeling) and late (6- to 24-hour postlabeling). The time course of release of fibronectin (Fn) and of angiotensin-converting enzyme (ACE) was determined by using immunoprecipitation. ACE appeared only after 6 hours of chase. Fn appeared throughout the chase period. The effects of serum and of the protease inhibitors alpha-2 macroglobulin, pepstatin, and leupeptin on protein release were examined. In the absence of serum, endothelial cell culture medium contained substantial protease activity capable of completely degrading most of the released proteins; a major effect of serum was to protect newly released protein from degradation.
mesh_terms: D000818:Animals; D001011:Aorta / Q000378:metabolism; D002478:Cells, Cultured; D004727:Endothelium; D007106:Immune Sera / Q000494:pharmacology*; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D011506:Proteins / Q000378:metabolism*; D013552:Swine; D013997:Time Factors
chemical_list: D007106:Immune Sera; D011480:Protease Inhibitors; D011506:Proteins; D007703:Peptidyl-Dipeptidase A