(+)-(3S,4R)-4-(N-Acetyl-N-benzyloxyamino)-6-cyano-3,4-dihydro-2,2- dimethyl- 2H-1-benzopyran-3-ol (Y-27152) is a new K+ channel opener with a long duration of action and less tachycardia. In this study, Y-27152 was compared with a K+ channel opener lemakalim and a Ca++ channel blocker nifedipine for antihypertensive activity in conscious spontaneously hypertensive rats (SHR) and two-kidney, one-clip renal hypertensive dogs (RHD). In conscious SHR, Y-27152 (0.1-1 mg/kg, p.o.) produced long-lasting dose-related decreases in systolic blood pressure. At 1 mg/kg, the maximum response occurred 5 to 7 hr after dosing, and 24 hr later, the pressure was still significantly reduced. Heart rate was not changed by these doses of Y-27152, whereas equihypotensive doses of lemakalim or nifedipine were strongly tachycardic. The cardiovascular effects of Y-27152 were antagonized by glibenclamide (20 mg/kg, i.v.). In conscious unrestrained RHD, Y-27152 at doses of 0.01, 0.03 and 0.1 mg/kg lowered blood pressure with a slow onset and long duration of action and had only a minimal effect on heart rate, whereas both lemakalim and nifedipine reduced blood pressure and markedly increased heart rate. No tolerance to the antihypertensive effect of Y-27152 (0.1 mg/kg) occurred during an 8-week repeated daily dosing to RHD and plasma renin activity, and aldosterone levels were not elevated during this period. In rat aortic rings contracted with 20 mM KCl, Y-27152 did not modify the tension; however, its desbenzyl form (Y-26763) produced vasorelaxation, and this effect was antagonized competitively by glibenclamide.(ABSTRACT TRUNCATED AT 250 WORDS)