title: Vitamin K-dependent synthesis and modification of precursor prothrombin in cultured H-35 hepatoma cells.
abstract: The ability of confluent monolayers of H-35 cells, originally obtained from a rat hepatoma, to synthesize prothrombin in response to vitamin K1 (phylloquinone) was studied. As demonstrated by radioimmunoassay, selective barium salt adsorption, and two coagulation assays which discriminate between precursor- and mature-prothrombin, these cells retained their ability to synthesize precursor prothrombin (preprothrombin) in the absence of exogenous phylloquinone (vitamin K). When phylloquinone was added to the medium (100 ng/ml), the existing intracellular concentration of preprothrombin was reduced to 50% within 1 hr after exposure to the vitamin and slowly declined thereafter to approximately 30% of control levels by 36 hr. Concomitant with the rapid loss of intracellular preprothrombin was the appearance of mature prothrombin in the medium. The appearance of prothrombin was biphasic: occurring during the initial 0-6 hr interval, and again at an increased rate during the next 18-24 hr interval. The amount of prothrombin appearing in the medium exceeded by severalfold the amount of precursor mobilized. These data demonstrate that monolayer cultures of H-35 hepatoma cells retain their ability to synthesize preprothrombin and other enzymes, responsible for post-translational modification of prothrombin and its subsequent secretion, under the influence of vitamin K.
mesh_terms: D001681:Biological Assay; D006528:Carcinoma, Hepatocellular; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D008113:Liver Neoplasms; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000378:metabolism*; D011516:Prothrombin / Q000096:biosynthesis* / Q000276:immunology; D012333:RNA, Messenger / Q000378:metabolism; D011863:Radioimmunoassay; D014158:Transcription, Genetic; D014812:Vitamin K / Q000494:pharmacology*
chemical_list: D007328:Insulin; D011498:Protein Precursors; D012333:RNA, Messenger; D014812:Vitamin K; D011516:Prothrombin