ALPHA(2)-ADRENOCEPTOR ACTIVATION INCREASES CALCIUM-CHANNEL CURRENTS IN SINGLE VASCULAR SMOOTH-MUSCLE CELLS ISOLATED FROM HUMAN OMENTAL RESISTANCE ARTERIES

Single cells were freshly isolated from human omental resistance arter ies using an enzymatic dispersion technique. Calcium channel currents (I-Ba) were recorded using whole cell voltage clamp techniques with Ba 2+ as the charge carrier. BHT 933, a selective alpha(2)-adrenoceptor a gonist, increased I-Ba. The effect of BHT 933 was reversible following washout. The action of BHT 933 was blocked by yohimbine. Pretreatment of tissues with pertussis toxin for 18 h or inclusion of GDP-beta-S i n the intracellular patch pipette solution also prevented the BHT 933- induced rise in I-Ba, but had no effect on I-Ba in the absence of BHT 933. Activation of alpha(2)-adrenoceptors in human vascular smooth mus cle cells increases I-Ba by a mechanism involving a pertussis toxin-se nsitive G protein.