Calcium channel blockers versus angiotensin-converting enzyme inhibitors: renal effects. Angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers are two classes of antihypertensive agents with novel effects on renal function. In both experimental and clinical studies, calcium channel blockers tend to increase renal blood flow, glomerular filtration rate, and urinary sodium excretion in essential hypertension. ACE inhibitors have similar effects on renal blood flow and glomerular filtration rate in essential hypertension, but they tend to cause sodium retention. ACE inhibitors can cause marked reductions in glomerular filtration rate in renovascular hypertension, making them a problematic choice for the treatment of this form of hypertension. In chronic, progressive renal diseases, ACE inhibitors have been shown to decrease protein excretion and morphologic evidence of glomerulosclerosis. The relationship of the decrease in protein excretion to the progression of renal disease has not yet been established. 