Zeneca ZD6169, (S^,)-N--(4-benzoylphenyl)-3,3,3-trifluoro-2-hydroxy-2-methylpropionamide, is a novel compound which relaxes urinary bladder smooth muscle in vitro. The effect of ZD6169 and two of its analogs on ⁸⁶Rb efflux and ³H-P1075 binding in guinea pig bladder strips was investigated to characterize the K-channel opening properties of this compound. ZD6169 concentration dependently increased the rate of ⁸⁶Rb efflux from guinea pig bladder strips. ⁸⁶Rb efflux evoked by ZD6169 and its analogs was blocked by glibenclamide (30 µM) but not by charybdotoxin, apamin or α-dendrotoxin, suggesting that this compound activates K_Atp channels in guinea pig bladder. In addition, interaction of ZD6169 with K_Atp channels was also confirmed in human bladder smooth muscle cells. Specific binding of ³H-P1075, a potent opener of K_Atp channels, to guinea pig urinary bladder strips was observed. ³H-P1075 binding was inhibited by known K_Atp openers. ZD6169 inhibited binding of ³H-P1075 to urinary bladder strips like other structurally different K_ATp openers, e.g. cromakalim and pinacidil. Potencies for inhibition of ³H-P1075 binding by ZD6169 and other potassium channel openers correlate well with potencies for increase in ⁸⁶Rb efflux and bladder muscle relaxation studies. It is concluded that Zeneca ZD6169 is a potassium channel opener which activates ATP-sensitive K-channels in guinea pig urinary bladder strips as well as in human bladder cells. Furthermore, binding studies suggest that the effects of ZD6169 and its analogs are mediated by binding to the site labeled by ³H-P1075 in guinea pig bladder strips.