Spatial changes of [Ca2+]i and contraction caused by phorbol esters in vascular smooth muscle cells
Nakajima, S.; Fujimoto, M.; Ueda, M.
American Journal of Physiology 265(4 Pt 1): C1138-C1145
1993
ISSN/ISBN: 0002-9513 PMID: 8238304 Document Number: 418147
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 Ca-2+ concentration ((Ca-2+)-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 Ca-2+ in localized peripheral regions, followed by expansion of this elevated Ca-2+ level throughout the cytoplasm. High K+ also induced a dynamic change of (Ca-2+)-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 (Ca-2+)-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 (Ca-2+)-i increase.