Effects of meclofenamate and captopril on blood flow to the kidney and spleen in conscious rabbits subjected to mild haemorrhage.
1. Regional haemodynamic responses to mild haemorrhage were studied in three groups each of seven conscious rabbits, in the presence of either buffer, the prostaglandin cyclo-oxygenase inhibitor meclofenamate, or the kininase II inhibitor captopril. 2. Renal and splenic vasoconstriction occurred with meclofenamate in haemorrhaged animals, and were accentuated by the subsequent administration of captopril. 3. Captopril alone caused mild renal vasodilatation, but subsequent administration of meclofenamate again caused vasoconstriction. 4. Flow to the adrenal coronary, cerebral and hepatic artery circulations was unaffected by meclofenamate or captopril after haemorrhage. 5. The results indicated that the enhanced vasopressor activity occurring during haemorrhage greatly increased the dependence on vasodilator prostaglandins of flow to the renal and splenic vascular beds. 6. The vasoconstrictor effect of meclofenamate does not appear to be due to unopposed action of angiotensin II when prostaglandin synthesis is suppressed.