Vanadate inhibits the calcium extrusion in rat pancreatic acinar cells

Our objective was to evaluate the role of vanadate on calcium extrusion in Fura-2-loaded rat pancreatic acinar cells by digital microscopic fluorimetr y and spectrofluorimetry. In the absence of extracellular calcium, perfusio n of pancreatic acinar cells with 1 nM CCK-8 and 1 mM vanadate did not sign ificantly affect the typical transient calcium spike induced by CCK-8, but the plateau phase of calcium in response to CCK-8 remained elevated. In add ition, vanadate was able to inhibit calcium efflux evoked by CCK-8 when we determined directly calcium transport across plasma membrane using Calcium Green-SN hexapotassium salt (cell impermeant form) in cell populations. The effect of vanadate on calcium extrusion was strongly blocked by the sulfhy dryl-reducing agent dithiothreitol (DTT). The present results demonstrate t hat vanadate is able to irreversibly inhibit the calcium extrusion. This ef fect of vanadate can be blocked using DTT, indicating that its action is pr obably mediated by oxidation of sulfhydryl groups of Ca2+-ATPases. (C) 2001 Elsevier Science Inc. All rights reserved.