DEPLETION AND REFILLING OF INTRACELLULAR CA2+ STORES INDUCE OSCILLATIONS OF CA2+ CURRENT

An agonist-induced Ca2+ influx pathway in vascular endothelium and other nonexcitable cells is closely aligned with the depletion of microsomal Ca2+ stores. The mechanism by which this occurs is unknown. In these studies 2',5',-di(tert-butyl-1,4-benzohydroquinone, a specific inhibitor of the microsomal Ca2+-adenosinetriphosphatase, and patch-clamp recordings were used to evaluate the relationship of inward Ca2+ current to the depletion of intracellular Ca2+ stores. The results demonstrate that depletion and refilling of Ca2+ stores control the amplitude of an electrogenic influx pathway in vascular endothelium. Prominent fluctuations in Ca2+ current occur when there is an imbalance between depletion and refilling of the stores. Furthermore, the studies suggest that the Ca2+ influx pathway is spatially in close association with the intracellular store.