Spatial changes of [Ca2+]i and contraction caused by phorbol esters in vascular smooth muscle cells.
In A7r5 smooth muscle cell suspensions, 12-deoxyphorbol 13-isobutyrate (DPB) and phorbol 12,13-dibutyrate (PDB), active phorbol esters for protein kinase C (PKC), increased the intracellular Ca2+ concentration ([Ca2+]i), but 4 alpha-PDB, an inactive phorbol ester, did not. Digital images of the fura 2 fluorescence from single cells revealed that DPB caused elevation of Ca2+ in localized peripheral regions, followed by expansion of this elevated Ca2+ level throughout the cytoplasm. High K+ also induced a dynamic change of [Ca2+]i. DPB and high K+ increased the wrinkles and distortions in the flexible growth surface beneath the cells. In Ca(2+)-depleted media, DPB did not affect [Ca2+]i but substantially increased wrinkles. The increase could be eliminated by staurosporine, a specific inhibitor of PKC. DPB increased the particulate PKC activity in a concentration-dependent manner. These results suggest that PKC activation induces cellular contractions through two distinct mechanisms, one dependent on and another independent of the [Ca2+]i increase.
Nakajima
S
S
Shionogi Research Laboratories, Osaka, Japan.
Fujimoto
M
M
Ueda
M
M
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D005456:Fluorescent Dyes; D005470:Fluorometry; D016257:Fura-2; D007091:Image Processing, Computer-Assisted; D007425:Intracellular Membranes / Q000378:metabolism*; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D009994:Osmolar Concentration; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D010703:Phorbol Esters / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism
D005456:Fluorescent Dyes; D010703:Phorbol Esters; C039067:12-deoxyphorbol 13-isobutyrate; D015240:Phorbol 12,13-Dibutyrate; D011493:Protein Kinase C; D002118:Calcium; D016257:Fura-2