Effects of meclofenamate and captopril on adrenal blood flow: contrasts in conscious rabbits at rest and after hemorrhage.

The role of prostaglandins and angiotensin II or kinins in maintaining adrenal blood flow was studied using the prostaglandin cyclo-oxygenase inhibitor meclofenamate and the kininase inhibitor captopril in resting and hemorrhaged (10 ml/kg) conscious rabbits. Meclofenamate (6 mg/kg intravenously) reduced adrenal blood flow after 3, 15 and 30 minutes by 26, 28 and 17 percent, respectively. Captopril increased adrenal flow by 20 percent, an effect subsequently reversed by meclofenamate. In contrast, hemorrhaged rabbits maintained adrenal blood flow following meclofenamate and captopril despite substantial reductions in renal blood flow with meclofenamate given before and after captopril. It is concluded that (1) adrenal blood flow at rest is modulated by vasodilator prostaglandins and to a lesser extent angiotensin II or bradykinin. (2) The adrenal effects of meclofenamate and captopril are overriden by hemorrhage, perhaps reflecting the need to increase adrenal hormones during hypovolemic stress. (3) The decrease in plasma catecholamines seen with meclofenamate at rest may be due to reduced adrenal blood flow.