Effects of trans- and cis-resveratrol on Ca2+ handling in A7r5 vascular myocytes

Although the natural polyphenol resveratrol posses a direct vasorelaxant effect, its effects on cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) in vascular cells remain still unclear. Here, we have investigated the effects of the isomers trans- and cis-resveratrol on agonist- and high-K(+)-induced [Ca(2+)](i) increases and on voltage-activated transmembrane Ca(2+) fluxes using imaging and patch-clamp techniques in vascular A7r5 myocytes. Arginine vasopressin (AVP) or angiotensin II caused a biphasic increase in [Ca(2+)](i) that was reduced by preincubation with trans-resveratrol and cis-resveratrol. Both isomers also reduced the agonist-induced increase in [Ca(2+)](i) in absence of extracellular Ca(2+). In high-K(+) Ca(2+)-free solution, reintroduction of Ca(2+) caused a sustained rise in [Ca(2+)](i) that was reduced by preincubation with trans-resveratrol or cis-resveratrol. When the isomers were applied during the plateau phase of the agonist- or the high-K(+)-induced response, a biphasic change in [Ca(2+)](i) was observed: a transient reduction of the plateau (<5 min) followed by an increase (>10 min). Finally, trans-resveratrol and cis-resveratrol inhibited voltage-dependent L-type Ca(2+) currents (I(Ca(L))). In conclusion, resveratrol isomers exert a dual effect on [Ca(2+)](i) handling in A7r5 myocytes: 1) a blockade of I(Ca(L)) and 2) an increase in [Ca(2+)](i) by depletion of intracellular Ca(2+) stores (which interferes with the agonist-induced release of intracellular Ca(2+)) and influx of Ca(2+), mainly due to activation of capacitative Ca(2+) entry, although other Ca(2+)-permeable channels are also involved. Taken together, these effects may explain, in part, the endothelium-independent vasorelaxant effects of resveratrol in rat aorta.