EFFECT OF CONVERTING ENZYME INHIBITION ON THE RENAL HAEMODYNAMIC RESPONSES TO NORADRENALINE INFUSION IN THE RAT

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Abstract
The renal haemodynamic responses to a close arterial infusion of noradrenaline (29.7–177.9 nmol kg−1h−1) were measured in rats anaesthetized with pentobarbitone. Systemic blood pressure was unaffected by noradrenaline infusion at this dose level. Renal blood flow was significantly reduced by 16% while glomerular filtration rate remained unchanged. These responses resulted in a rise in filtration fraction of some 10%. In a separate group of animals, noradrenaline infusion in this manner and at a similar dose rate increased plasma renin activity approximately 3 fold. Continuous infusion of the angiotensin converting enzyme inhibitor, teprotide (3.36 μmol kg−1h−1), had no measurable effect on systemic blood pressure, renal blood flow, glomerular filtration rate or filtration fraction. Infusion of noradrenaline into these animals receiving teprotide caused a significant fall in renal blood flow of 16%. There was a fall in glomerular filtration rate of some 17% which was significantly different from the response observed in the animals not receiving teprotide. There was a consequent small but insignificant fall in filtration fraction. These data show that the regulation of glomerular filtration rate in response to the vasoconstrictor drug, noradrenaline, is partly mediated via the renin‐angiotensin system. They provide evidence for a role of intrarenal angiotensin II in regulating glomerular filtration by causing efferent arteriolar vasoconstriction.

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