Inhibition of bradykinin of the vascular effects of pressor hormones in the canine kidney: relationship to prostaglandins.

1. Renal arterial injection of bolus doses of angiotensin II or noradrenaline, (0.06, 0.12 and 0.25 microgram) caused renal vasoconstriction and decreased blood flow to the kidney in a dose-related manner in dogs anaesthetized by sodium pentobarbital. 2. The effect of angiotensin II and noradrenaline in lowering renal blood flow was reduced during renal arterial infusion of either bradykinin (10 ng min-1 kg-1) or prostaglandin E2 (4 ng min-1 kg-1). 3. Pretreatment of the dogs with an inhibitor of prostaglandin synthesis, sodium meclofenamate (5 mg/kg), blunted the inhibitory action of bradykinin, but not that of prostaglandin E2, on renal vascular reactivity to angiotensin II and noradrenaline. 4. These results indicate that bradykinin reduces the renal vasoconstriction induced by angiotensin II and noradrenaline in the dog by a mechanism dependent upon synthesis of prostaglandins.