[CAS NO. 88-58-4]  BHQ

2,5-Di-t-butyl-1,4-benzohydroquinone (BHQ) has been described as a rather selective sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) inhibitor. However, BHQ is not very specific, as it hits other sites of action besides SERCA. BHQ is shown, in fact, to reduce passive Ca2+ leakage from internal stores of permeabilized A7r5 vascular smooth muscle cells and to inhibit plasma membrane Ca2+ influx in parotid acinar cells, rat thymic lymphocytes, and GH3 pituitary cells. BHQ affects both endothelial and smooth muscle functions in rat aorta rings in vitro. BHQ induces endothelium-dependent relaxation by stimulating the NO synthase pathway, via activation of Ca2+ influx through Ni2+-sensitive Ca2+ channels in the endothelial cells. BHQ exhibits pleiotypic effects on rings deprived of endothelium by inducing both a myotonic response, dependent on the activation of Ca2+ influx via a Ni2+-sensitive pathway, and a myolytic effect, possibly dependent on either the depletion of intracellular Ca2+ stores or antagonism of Ca2+ entry via L-type Ca2+ channels. BHQ is a lipophilic, membrane permeable molecule, capable of generating superoxide anion at both sides of the plasmalemma.