Monovalent cation dependence of tissue plasminogen activator synthesis by HeLa cells.
HeLa cells synthesize and secrete increased levels of tissue plasminogen activator (tPA) when incubated for 18 h with 10-20 nM phorbol myristate acetate. This response was inhibited by a number of conditions which affect intracellular Na+ and K+ concentrations. Removing extracellular Na+, while maintaining isotonicity with choline+, reduced the secretion of both functional and antigenic tPA in a linear fashion. A series of cardiac glycosides and related compounds strongly inhibited tPA secretion with the following rank order of potency: digitoxin = ouabain greater than digoxin greater than digitoxigenin greater than digoxigenin greater than digitoxose greater than digitonin. These compounds also inhibited cellular Na+/K+-ATPase activity over an identical concentration range. Two compounds which selectively increase cellular permeability to K+, valinomycin, and nigericin, strongly inhibited tPA secretion, with IC50 values of approximately 50 nM. In contrast, monensin, which selectively increases cellular permeability to Na+, was much less active. Valinomycin, but not nigericin, also inhibited cellular Na+/K+-ATPase activity. Phorbol myristate acetate, 5-20 nM, increased Na+/K+-ATPase activity up to 2-fold and tPA secretion up to 15-fold. We conclude that the secretion of tPA by HeLa cells treated with phorbol myristate acetate proceeds via a mechanism which requires extracellular Na+ and a functional Na+/K+-ATPase ("sodium pump") enzyme.
D002414:Cations, Monovalent; D002463:Cell Membrane Permeability / Q000187:drug effects; D006367:HeLa Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008985:Monensin / Q000494:pharmacology; D009550:Nigericin / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010959:Tissue Plasminogen Activator / Q000096:biosynthesis*; D014634:Valinomycin / Q000494:pharmacology
D002414:Cations, Monovalent; D014634:Valinomycin; D010042:Ouabain; D008985:Monensin; D012964:Sodium; D010959:Tissue Plasminogen Activator; D000254:Sodium-Potassium-Exchanging ATPase; D013755:Tetradecanoylphorbol Acetate; D009550:Nigericin; D011188:Potassium