OBJECTIVE Our null hypothesis was that the angiotensin II antagonist saralasin does not reduce the number of ovulations in the rat ovarian perfusion model. METHODS Ovaries from pregnant mare's serum gonadotropin-stimulated immature rats were perfused with nutrient media to which luteinizing hormone and 3-isobutyl-1-methylxanthine had been added to induce ovulation. Test perfusions were treated with saralasin 1 mumol/L (n = 0.5) and compared with controls (n = 5) with the Student t test. Perfusions with both saralasin and angiotensin II and dose-response evaluations were performed. RESULTS Saralasin-treated ovulations were 6.6 +/- 1.3 (mean + SEM) compared with 18.6 +/- 3.9, p < 0.02. The effects of saralasin could be reversed with the addition of an equimolar amount of angiotensin II. Dose-response evaluations showed a progressive inhibition of ovulation at 10(-8) to 10(-6) mol/L. CONCLUSIONS The angiotensin II antagonist saralasin inhibits ovulation in a dose-dependent fashion; this effect is canceled by the addition of equimolar concentrations of angiotensin II.