title: Biosynthesis of coagulation Factor V by a human hepatocellular carcinoma cell line.
abstract: A human hepatocellular carcinoma line, HepG2, was found to secrete coagulation Factor V. Factor V activity in HepG2 culture fluid increased nearly linearly during a 20-h time course (5 ng Factor Va/h per 10(6) cells). Thrombin treatment increased Factor V activity in HepG2 culture medium six- to ninefold, indicating that the medium accumulates a mixture of Factors V and Va. To demonstrate de novo synthesis of Factor V, HepG2 cells were incubated in culture medium containing [35S]methionine. Labeled Factor V was immunoprecipitated from the medium and was shown to co-migrate with purified plasma Factor V upon sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography. When medium was treated with thrombin before immunoprecipitation and fluorography, the 330,000-Mr [35S]methionine-labeled Factor V was converted to Factor Va. Factor Va coagulant activities from HepG2 cells and human plasma were inhibited in parallel by anti-Factor V antibody, indicating that HepG2 and plasma Factor Va have the same intrinsic activity. If normal hepatocytes synthesize Factor V at the same rate as HepG2 cells, then hepatocyte secretion can account for the total Factor V present in plasma. The production of Factor V by cultured human umbilical vein endothelial cells was also examined. Spent culture medium from endothelial cells contained only Factor Va and the amount was less than 1% of the activity found in medium from HepG2 cells under comparable conditions. The amount of Factor V activity in endothelial cell culture fluid did not change with time in culture.
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002460:Cell Line; D004727:Endothelium / Q000378:metabolism; D000939:Epitopes / Q000276:immunology; D005165:Factor V / Q000096:biosynthesis* / Q000276:immunology / Q000378:metabolism; D015943:Factor Va; D006801:Humans; D007163:Immunosorbent Techniques; D007700:Kinetics; D008113:Liver Neoplasms; D013917:Thrombin / Q000494:pharmacology; D014471:Umbilical Veins / Q000378:metabolism
chemical_list: D000939:Epitopes; D015943:Factor Va; D005165:Factor V; D013917:Thrombin