Effects of renal nerve stimulation, norepinephrine and angiotensin II on renal blood flow in relation to release of PG-like substances in anesthetized dogs.

The effects of vasoconstrictor stimulation, renal nerve stimulation or infusion of norepinephrine or angiotensin II into the renal artery, on renal blood flow were determined before and after the administration of indomethacin in pentobarbital-anesthetized dogs. When the renal blood flow was allowed to vary, in control responses, an initial rapid reduction was followed by a return to the control level, despite the continued application of vasoconstrictor stimulation. After the intravenous administration of indomethacin, a prostaglandin synthetase inhibitor, the recovery response was markedly diminished. Prostaglandin-like substances in renal venous blood were determined by bioassay of blood extracts, using rat fundus strips. Indomethacin suppressed the increase in the level of these substances during the application of vasoconstrictor stimulators. Our results indicate that renal prostaglandin-like substances are released during vasoconstrictor stimulation; under the present experimental conditions, this release blunts the effect of the stimuli.