[Inhibition of the angiotensin-converting enzyme--effect on kidney function and electrolyte balance]

Inhibition of the angiotensin converting enzyme (ACE) is associated with a decrease in renal vascular resistance, an increase in renal blood flow and a redistribution of intrarenal blood flow toward juxtamedullary nephrons. In general, ACE-inhibition does not affect normal glomerular filtration rate (GFR) but may increase GFR in patients on a low sodium intake prior to treatment. Since the rise in GFR is smaller than the rise in renal blood flow, in most instances a decrease in filtration fraction will result. In contrast to other vasodilator drugs, the decrease in blood pressure induced by ACE-inhibition is not accompanied by sodium retention, but rather by an initial natriuresis. ACE-inhibition also prevents secondary aldosteronism and thereby avoids renal potassium loss. The initial positive potassium balance after ACE-inhibition may protect patients with heart disease from potentially hazardous arrhythmias. Redistribution of intrarenal blood flow with increased medullary flow, in addition, will antagonize the hydrosmotic effect of vasopressin and thus result in a rise in free-water clearance. Finally, based on experimental evidence, long-term treatment with ACE-inhibitors may have a protective effect on renal function by reducing glomerular filtration pressure.