title: A role for ornithine in the regulation of putrescine accumulation and ornithine decarboxylase activity in Reuber H35 hepatoma cells.
abstract: We investigated the ability of intracellular ornithine to alter both the biosynthesis of putrescine and the activity of ornithine decarboxylase in Reuber H35 hepatoma cells in culture incubated with 12-O- tetrade - canoylphorbol 13-acetate (TPA). In confluent cultures of H35 cells, the addition of TPA (1.6 microM) caused the activity of ornithine decarboxylase to increase by more than 100-fold within 4 h. When exogenous ornithine (0.1-1.0 mM) was added to the culture medium with TPA, a marked dose-dependent increase in the production of putrescine was observed. The activity of ornithine decarboxylase in the same cultures incubated with ornithine decreased in a similar dose-dependent manner. The addition of arginine (0.1-1.0 mM) (but not lysine or histidine) to the H35 cells in culture concomitant with TPA also led to a relative increase in putrescine biosynthesis and a decrease in ornithine decarboxylase activity compared to cultures not receiving the amino acids. A similar response to exogenous ornithine and TPA was observed in a series of less confluent rapidly growing cultures which were in culture for a shorter period of time. The confluent cultures possessed a basal level of arginase (55 units/mg protein) which increased approx. 2-fold upon treatment with TPA. The intracellular concentration of ornithine in the unstimulated cells was in the order of 0.02-0.03 mM. Upon incubation of the cells with exogenous ornithine or arginine, the intracellular pools of these amino acids increased 4- to 8-fold.
mesh_terms: D000818:Animals; D001119:Arginase / Q000378:metabolism; D001120:Arginine / Q000378:metabolism / Q000494:pharmacology; D002448:Cell Adhesion; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D009952:Ornithine / Q000502:physiology*; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D011700:Putrescine / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D001120:Arginine; D009952:Ornithine; D001119:Arginase; D009955:Ornithine Decarboxylase; D013755:Tetradecanoylphorbol Acetate; D011700:Putrescine