CL 115,347 orally (0.25-10 mg/kg) and topically (0.03 and 0.1 mg/kg) lowered blood pressure in a dose-dependent manner in conscious spontaneously hypertensive rats (SHR). Duration of action of the oral dose range was from 1 to more than 8 h and of the topical dose range, from more than 6 to more than 24 h. CL 115,347 was 100-200 times more potent orally and greater than 250 times more potent topically than l-prostaglandin (PG) E2. When 3 mg/kg was administered orally, CL 115,347 was also active in Dahl "S" salt-sensitive hypertensive rats, deoxycorticosterone acetate-salt hypertensive rats, aorta-coarcted renin-dependent hypertensive rats, normotensive rats, bilaterally nephrectomized SHR, and bilaterally ureteral-ligated SHR. CL 115,347 was also orally active at 0.1 mg/kg in normotensive rhesus monkeys and in renal hypertensive dogs at 1 mg/kg. CL 115,347 was as active as l-PGE2 in relaxing the rabbit ear arterial smooth muscle in vitro. In anesthetized dogs, CL 115,347 injected intra-arterially (0.5-10 micrograms) into the vascular bed being studied increased blood flow to femoral, carotid, coronary, superior mesenteric, and renal vascular beds. CL 115,347 decreased vasopressor responses induced by electrical stimulation of the spinal cord at T7-T9 but did not decrease the tachycardia induced by stimulation of the cardioaccelerator segments (C7-T1) in pithed SHR. CL 115,347 has a broad spectrum of antihypertensive activity in various animal models and probably exerts its major antihypertensive effects through relaxation of blood vessels.