Contrasting Effects of the Renin–Angiotensin System on Renal Function Disclosed During Converting Enzyme Inhibition in Patients with Renal Hypertension

In three unilaterally nephrectomized patients with a poorly functioning remaining kidney, a reversible decrease of glomerular filtration rate (GFR) was observed during treatment with captopril. Only modest decreases in blood pressure occurred. In four patients with various forms of malignant hypertension and impairment of renal function, GFR remained unchanged or even increased when the blood pressure was reduced by captopril. All patients had increased plasma concentrations of renin and angiotensin II prior to captopril. We hypothesize that an activation of the renin-angiotensin system in hypertensive patients with reduced GFR may either reflect a compensatory mechanism aiming at maintaining renal function, or imply an excessive angiotensin-mediated vasoconstriction causing a decrease in renal function. The use of angiotensin converting enzyme inhibitors may be damaging for renal function in the first situation and beneficial in the second.