Different protein kinase C isozymes could modulate bradykinin-induced extracellular calcium-dependent and -independent increases in osteoblast-like MC3T3-E1 cells.
Effects of protein kinase C (PKC) on bradykinin (BK)-induced intracellular calcium mobilization, consisting of rapid Ca2+ release from internal stores and a subsequent sustained Ca2+ inflow, were examined in Fura-2-loaded osteoblast-like MC3T3-E1 cells. The sustained Ca2+ inflow as inferred with Mn2+ quench method was blocked by Ni2+ and a receptor-operated Ca2+ channel blocker SK&F 96365, but not by nifedipine. The short-term pretreatment with phorbol 12-myristate 13-acetate (PMA), inhibited BK-stimulated Ca2+ inflow, and the prior treatment with PKC inhibitors, H-7 or staurosporine, enhanced the initial internal release and reversed the PMA effect. Moreover, 6 h pretreatment with PMA caused similar effect on the BK-induced inflow to that obtained with PKC inhibitors, whereas 24 h pretreatment was necessary to affect the internal release. On the other hand, the translocation and down-regulation of PKC isozymes were examined after PMA treatment of MC3T3-E1 cells by immunoblot analyses of PKCs with the isozyme-specific antibodies. 6 h treatment with PMA induced down-regulation of PKC beta, whereas longer treatment was needed for down-regulation of PKC alpha. Taken together, it was suggested that the BK-induced initial Ca2+ peak and the sustained Ca2+ inflow through the activation of a receptor-operated Ca2+ channel, are differentially regulated by PKC isozymes alpha and beta, respectively, in osteoblast-like MC3T3-E1 cells.
Sakai
T
T
Department of Oral and Maxillo-Facial Surgery, Gifu University School of Medicine, Japan.
Okano
Y
Y
Nozawa
Y
Y
Oka
N
N
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D015220:Calcium Channels / Q000201:enzymology / Q000378:metabolism; D002460:Cell Line; D015536:Down-Regulation / Q000187:drug effects; D005110:Extracellular Space / Q000187:drug effects / Q000502:physiology; D016257:Fura-2; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008345:Manganese / Q000378:metabolism; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D015220:Calcium Channels; D007527:Isoenzymes; D008345:Manganese; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2