2,5-Di-tert-butylhydroquinone (BHQ) is an effective and selective endoplasmic reticulum Ca2+-ATPase inhibitor.

Ca2+-ATPase:66.7 μM

2,5-Di-tert-butylhydroquinone shifted the voltage dependence of the steady-state inactivation curve to more negative potentials by 7 mV in the mid-potential of the curve, without affecting the activation curve as well as the time course of I(Ca(L)) inactivation.Preincubation of the cells either with 10 microM cyclopiazonic acid, a SERCA inhibitor, or with 3 mM diethyldithiocarbamate, an inhibitor of intracellular superoxide dismutase (SOD), did not modify 2,5-Di-tert-butylhydroquinone inhibition of I(Ca(L)).On the contrary, this effect was no longer evident when SOD (250 u ml(-1)) was added to the perfusion medium.Either in the presence or in the absence of cells, 2,5-Di-tert-butylhydroquinone gave rise to superoxide anion formation, which was markedly inhibited by the addition of SOD.At micromolar concentrations, 2,5-Di-tert-butylhydroquinone inhibits vascular I(Ca(L)) by giving rise to the formation of superoxide anion which in turn impairs the channel function.