Renal vascular effects of angiotensin II, arginine-vasopressin and bradykinin in rats: interactions with prostaglandins.

1. The renal vascular responses to the peptide hormones angiotensin II (ANG II), arginine-vasopressin (AVP) and bradykinin (BK) were studied in anaesthetized rats with flow-meter techniques. The contribution of prostaglandins (PG) to their renal vascular effects was assessed with the aid of the PG-synthesis inhibitor indomethacin. 2. ANG II and AVP induced a dose-dependent increase in renal vascular resistance (RVR). The renal vasoconstrictor effects of both peptides were significantly augmented in rats pretreated with indomethacin. Indomethacin alone induced an increase in RVR, but not in mesenteric vascular resistance (MVR). 3. BK in low doses (1 micrograms/kg . min) tended to decrease RVR but increased RVR in high doses (20 micrograms/kg . min). MVR was reduced after all doses. The renal vasoconstrictor effect of BK was not affected by the ANG II-antagonist saralasin but almost completely blocked by indomethacin. 4. These results suggest that in the rat, as in other animal species and in man, renal PG's attenuate the renal effects of vasoconstrictor hormones such as ANG II and AVP. Although it has no such effect in other species. BK in high doses induces renal vasoconstriction in the rat, which appears also to be mediated by PG's. This response might be peculiar to the rat, since PG's act as renal vasodilators in other species.