European Journal of Pharmacology 1992-12-01

2,5-Di-(tert-butyl)-1,4-benzohydroquinone and cyclopiazonic acid decrease the Ca2+ permeability of endoplasmic reticulum.

L Missiaen, H De Smedt, G Droogmans, R Casteels

Index: Eur. J. Pharmacol. 227(4) , 391-4, (1992)

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Abstract

Specific inhibitors of the endoplasmic-reticulum Ca2+ pump will deplete intracellular stores and are therefore useful to study the role of store depletion on plasma-membrane Ca2+ permeability. We now report that the Ca(2+)-pump inhibitor 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBuBHQ) reduces the passive Ca2+ leak from the internal stores in permeabilized A7r5 vascular smooth-muscle cells. This aspecific effect occurred at concentrations that are normally used to empty the stores in intact cells. Cyclopiazonic acid exerted a similar, although less pronounced effect, while thapsigargin did not affect the passive Ca2+ leak. The inositol 1,4,5-trisphosphate-mediated Ca2+ release was not affected. tBuBHQ and cyclopiazonic acid cannot therefore be used as specific tools to probe the mechanism of receptor-mediated Ca2+ entry.