1. Studies were made of the effects on responses to vasoconstrictor agents of prostaglandins released from Krebs perfused isolated kidneys of genetic hypertensive and normotensive rats.
2. Prostaglandin E-like activity, detected by bio-assay, was released from kidneys of both groups of rats during the vasoconstriction produced by noradrenaline, angiotensin or prostaglandin F2α.
3. In preparations obtained from hypertensive rats, responses to higher doses of noradrenaline or angiotensin were initially greater than those from normotensive rats and these were then reduced to a greater extent by infusion of indomethacin, which abolished release of prostaglandin E-like activity. Thereafter, in kidneys of either group, vasoconstriction to noradrenaline was potentiated by infusion of prostaglandin E2.
4. We conclude that, in rats, renal prostaglandins released in response to vasoconstrictor agents could augment the effect of such agents and in genetic hypertensive rats release of renal prostaglandins could contribute to the disease.