Role of prostaglandin and angiotensin II in ANP-induced natriuresis.

The aim of the present study was to examine if the natriuresis induced by a dose of ANP that does not alter glomerular filtration rate (GFR) or mean arterial pressure (MAP) is accompanied by changes in renin release urinary excretion of prostaglandins and intrarenal blood flow distribution. It was found that the intrarenal infusion of ANP (8-33) at a dose of 0.05 micrograms/kg min in seven anaesthetized dogs did not produce any change in GFR or MAP, but its natriuretic effect was similar to that induced by a larger dose (0.3 micrograms/kg min, n = 5) that produces significant changes in both MAP and GFR. The natriuresis induced by the lower dose of ANP was associated with a redistribution of RBF to the deep cortical nephrons and with an increase (p less than 0.05) in urinary excretion of prostaglandins E2 and 6 keto-F1 alpha. Renin secretion rate decreased by a 54% (p less than 0.05). The role of angiotensin II (AII) suppression on the natriuresis induced by ANP was examine in another experimental group (n = 6). It was found that the infusion of ANP during fixed intrarenal levels of AII produced a natriuretic effect that was significantly lower (38%) than that produced by the infusion of ANP alone. The results of this study show that the natriuresis induced by ANP is not necessarily produced by an increase in GFR and is associated with a redistribution of RBF to the deep cortex an increase in urinary excretion of prostaglandins and a decrease of renin release. These results also suggest that the natriuretic effect of ANP is partly mediated by the intrarenal suppression of AII.