Angiotensin converting enzyme inhibition and renin release from the kidney

Experiments were performed in anaesthetized cats, to determine whether renal nerves interfere with the negative feedback action of angiotensin II (Ang II) on renin release. The increase in renin release from the innervated kidney in response to captopril-induced inhibition of Ang II generation was compared with the response of the contralateral denervated kidney. Renin release was measured before (control), and 5, 15 and 30 min after the beginning of captopril infusion (1 mg/kg priming dose followed by 1 mg/kg per h for 30 min intravenously), and 60 min after the end of the infusion. During the captopril treatment renin release from both kidneys increased, but after 15 and 30 min the increase in renin release from the innervated kidneys was significantly larger than that observed in the denervated kidneys. After the captopril infusion was stopped, renin release from both kidneys returned towards control values. These results could not be explained on the basis of the changes in renal haemodynamics, excretory functions and efferent renal nerve activity observed during the captopril infusion. The data suggest that the renal nerves influence the changes in renin release caused by captopril by increasing the sensitivity of juxtaglomerular cells to the negative feedback action of Ang II.