AJP - Cell Physiology, Vol 266, Issue 6 C1560-C1567, Copyright © 1994 by American Physiological Society

ARTICLES

Regulation of endothelin-induced Ca2+ mobilization in smooth muscle cells by protein kinase C

Y. T. Xuan, O. L. Wang and A. R. Whorton
Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina 27710.

We have investigated the role of protein kinase C (PKC) in regulating vascular smooth muscle cell responses to endothelin (ET). During the initial phase of the response, ET stimulated rapid formation of diacylglycerol due to rapid and transient activation of phosphatidyl inositol-specific phospholipase C and to rapid and prolonged activation of phospholipase D. Concurrently, ET stimulated translocation of PKC activity that reached a peak at 1 min and remained elevated for at least 20 min. Activation of PKC produced early inhibitory effects. Treatment of cells with phorbol 12-myristate 13-acetate (PMA) 5 min before stimulation with ET inhibited total inositol phosphate formation by > 50%. Because each inositol phosphate isomer was equally affected, the target appears to be either phospholipase C or some upstream component of the receptor coupling mechanism. Activation of PKC was important for sustained response to ET. Treatment of cells with staurosporine significantly reduced sustained elevation of cytosolic free Ca2+ concentration ([Ca2+]i) normally seen with ET. We had previously shown that sustained elevation of [Ca2+]i initiated by ET was due to continued activity of L-type Ca2+ channels. Our current data suggest that PKC is important in this response. For example, staurosporine inhibited both ET-induced 45Ca2+ and Mn2+ entry occurring 10 min after stimulation of influx mechanisms by the agonist. Similarly, pretreatment of cells for 18 h with phorbol dibutyrate depleted the cells of PKC and blocked the sustained activity of Ca2+ entry mechanisms stimulated by ET. Finally, PMA initiated a slowly developing, sustained elevation of [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)

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