The cardiovascular responses to intravenous administration of an isosterically modified prostaglandin (PG) analog, (+)-4-(3-[3-[2-(1-hydroxycyclohexyl)-ethyl]-4-oxo-thiazolidinyl]-propyl) benzoic acid, were determined in open-chest, anesthetized dogs. These responses were compared to responses with the naturally occurring prostaglandings, PGD2 and PGI2, and vasodilators, hydralazine, sodium nitroprusside, nifedipine and verapamil. Following administration of 5, 20 and 100 micrograms/kg PG analog, total peripheral resistance was significantly decreased from 74 +/- 2 to 59 +/- 6, 37 +/- 5 and 24 +/- 1 mmHg/l per min, respectively. Cardiac output was increased by the highest dose of PG analog; however, heart rate, left ventricular contractility and left ventricular end diastolic pressure were not changed. This profile of cardiac and vascular responses was similar to responses with PGI2 and hydralazine suggesting that PG analog is a potent arterial vasodilator with no direct effect on cardiac function.