AJP - Heart and Circulatory Physiology, Vol 255, Issue 6 1549-H1553, Copyright © 1988 by American Physiological Society

ARTICLES

ACh-induced calcium transients in primary cultures of rabbit aortic endothelial cells

N. R. Danthuluri, M. I. Cybulsky and T. A. Brock
Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts.

Acetylcholine (ACh) causes vascular smooth muscle relaxation by releasing endothelium-derived relaxing factor (EDRF) from endothelial cells (EC). Although a pivotal role for cytosolic free Ca2+ ([Ca2+]i) has been implicated in the generation and/or release of EDRF by various agonists, there is no conclusive evidence showing that ACh increases [Ca2+]i in EC. In the present study, using the Ca2+-sensitive fluorescent indicator fura-2, we show for the first time that ACh (10(-5) M) increases [Ca2+]i six- to sevenfold above prestimulus levels in primary cultures of rabbit aortic EC (RbAEC). ACh effects are dose dependent [effective concentration producing 50% of the maximum response (EC50) approximately 9 X 10(-7) M] and are blocked by atropine, a selective muscarinic receptor antagonist. The [Ca2+]i increase is due both to the mobilization of intracellular Ca2+ and to the influx of extracellular Ca2+. A 5-min incubation of RbAEC with 4 beta-phorbol 12-myristate 13-acetate (10(-7) M) inhibits ACh-induced [Ca2+]i transients, suggesting that the signaling pathway involved in ACh receptor signal transduction may be modulated via protein kinase C. These cultured EC provide a unique in vitro model system for studying mechanisms involved in ACh-induced EDRF release.

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