Haemodynamic regulation of renal prostaglandin and renin release

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Abstract
To examine the relationship between renal release of the prostaglandins E2(PGE2) and I2(PGI2) and renin during autoregulatory vasodilation, experiments were performed in anaesthetized dogs with denervated kidneys. Autoregulatory vasodilation was induced by reducing renal arterial pressure (RAP) or by raising ureteral pressure in steps. During progressive renal arterial constriction, PGE2and PGI2release reached maximal values (10.6±1.7 for PGE2and 6.6±1.1 pmol min‐1for PGI2release) at RAP of 7–80 mmHg, associated with almost no increase in renin release. By further reduction of RAP, prostaglandin release was not significantly altered, whereas renin release reached maximal values (18.7 ± 2.4μg AI min‐1) when autoregulatory vasodilation was complete at RAP below 55–60 mmHg. During progressive elevation of ureteral pressure, the release of PGE2, PGI2and renin increased in concert in a curvilinear fashion, reaching maximal values at a ureteral pressure of 85 mmHg. There was no further increase during ureteral occlusion and the plateau values averaged 23.6 ± 3.7 pmol min‐1for PGE2, 8.0±1.6pmol min‐1for PGI2and 16.6 ± 3.4μg A1 min‐1for renin. We conclude that vascular dilation enhances both prostaglandin and renin release. During reduction of RAP, preglomerular arteries are dilated at higher RAP than are afferent arterioles. Release of prostaglandins synthetized in arteries consequently occurs at higher RAP than release of renin, which is not enhanced until afferent arterioles ultimately dilate at RAP approaching 60 mmHg. In contrast, elevation of ureteral pressure provides nearly uniform enhancement of prostaglandin and renin release, indicating a more uniform dilation of the whole preglomerular vascular tree.