Single cells were freshly isolated from human omental resistance arteries using an enzymatic dispersion technique. Calcium channel currents (IBa) were recorded using whole cell voltage clamp techniques with Ba2+ as the charge carrier. BHT 933, a selective α2-adrenoceptor agonist, increased IBa. 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-β-S in the intracellular patch pipette solution also prevented the BHT 933-induced rise in IBa, but had no effect on IBa in the absence of BHT 933. Activation of α2-adrenoceptors in human vascular smooth muscle cells increases IBa by a mechanism involving a pertussis toxin-sensitive G prote