CONTRASTING EFFECTS OF CALCIUM-CHANNEL BLOCKADE VERSUS CONVERTING-ENZYME INHIBITION ON PROTEINURIA IN AFRICAN-AMERICANS WITH NON-INSULIN-DEPENDENT DIABETES-MELLITUS AND NEPHROPATHY

Hypertension is a common finding in non-insulin-dependent diabetes mel litus (NIDDM) nephropathy. African Americans have a high prevalence of NIDDM and hypertension, and are relatively resistant to the antihyper tensive effects of converting enzyme inhibitors (CEI) but respond well to calcium channel blockers (CCB). In the long-term study presented h ere, the effects of isradipine, a dihydropyridine calcium antagonist, on the course of the nephropathy were investigated and compared with t he effects of captopril in 31 African Americans with NIDDM and protein uria (greater than or equal to 500 mg/day). The patients were stratifi ed by levels of GFR and proteinuria, and they were randomized to recei ve isradipine (N = 16) or captopril (N = 15); doses were adjusted to m aintain similar BP levels (<140/90). At 6 months, mean arterial pressu re was similar (102 +/- 3 and 104 +/- 3 mm Hg in the isradipine and ca ptopril groups, respectively) and GFR was unchanged (Delta = -4 +/- 3 and +1 +/- 3 ml/min/1.73 in the isradipine and captopril groups, respe ctively; P = NS). However, proteinuria in the isradipine group increas ed by approximately 50% (2.01 +/- 0.40 versus 3.04 +/- 0.70 mg/mg crea tinine at baseline versus 6 months, respectively, P < 0.05), whereas c aptopril reduced proteinuria by 30% after 6 months (2.85 +/- 0.70 at b aseline versus 2.30 +/- 0.70 mg/mg creatinine, P < 0.05). Dietary prot ein, sodium intake, and HbA(1C) levels were similar in both groups and did not differ from baseline. It was concluded that over 6 months, ca ptopril reduces and isradipine increases proteinuria in African Americ ans with NIDDM and nephropathy. Whether this contrasting effect on pro teinuria will result in different rates of progression is not known, b ut dihydropyridine CCB should be used cautiously in African Americans with diabetic nephropathy.