title: ATP-induced entry of calcium in thyroid FRTL-5 cells. Studies with phorbol myristate acetate and thapsigargin.
abstract: Receptor-mediated Ca2+ entry was investigated in fura-2-loaded thyroid FRTL-5 cells. Activation of protein kinase C (PKC) by phorbol myristate acetate (PMA) attenuated the ATP-induced increase in intracellular free Ca2+ ([Ca2+]i). In PKC down-regulated cells, the ATP-induced increase in [Ca2+]i was increased compared with control cells. This enhanced increase in [Ca2+]i was apparently dependent on extracellular Ca2+, as no difference was observed between control cells and PKC down-regulated cells in Ca(2+)-free buffer. Addition of Ca2+ to cells stimulated with ATP in Ca(2+)-free buffer rapidly increased [Ca2+]i. The increase was blocked by PMA. However, PKC down-regulation had no effect on the [Ca2+]i response. Stimulating FRTL-5 cells with thapsigargin increased [Ca2+]i. Addition of ATP after thapsigargin had almost no effect on [Ca2+]i. In PKC down-regulated cells, addition of ATP after thapsigargin evoked a substantial increase in [Ca2+]i which was dependent on extracellular Ca2+. The results indicate that PKC has a modulatory effect on the ATP-induced entry of Ca2+ in FRTL-5 cells.
authors.affiliation: Endocrine Research Laboratory, University of Helsinki, Minerva Foundation Institute for Medical Research, Finland.
authors.forename: K
authors.initials: K
authors.lastname: Törnquist
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013729:Terpenes / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D019284:Thapsigargin; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism
chemical_list: D007093:Imidazoles; D013729:Terpenes; D015759:Ionomycin; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium