Graded effects of saralasin on prostaglandin E, plasma renin activity and renal blood flow in anaesthetized dogs

The objective of this study was to examine in anaesthetized dogs the graded effect of saralasin on renal prostaglandin E (PGE) release and to attempt to associate this change with its effects on plasma renin activity and renal blood flow. Blood pressure and renal blood flow were monitored. Renal PGE concentration and plasma renin activity were measured by radioimmunoassay. Saralasin or saline vehicle was infused into the renal artery for 20 min. Infusion of saralasin at the lowest dose of 0.25 micrograms/kg per min or saline vehicle did not alter either renal blood flow or plasma renin activity. Saralasin increased renal blood flow and caused a complete blockade of the renal vasoconstrictor response to exogenous angiotensin II at the two higher doses used (0.5 and 1 micrograms/kg per min). Only the highest dose of saralasin increased plasma renin activity significantly. Renal venous PGE concentration at the 5, 10 and 20 min periods of infusion was not changed significantly by any of these three doses of saralasin. We conclude therefore that the increases in renal blood flow and plasma renin activity caused by saralasin in the anaesthetized dog occur by mechanisms independent of changes in renal PGE.