EFFECT OF NIFEDIPINE, CAPTOPRIL AND PRAZOSIN ON SECRETORY FUNCTION OFPANCREATIC BETA-CELLS IN HYPERTENSIVE PATIENTS WITH TYPE-2 (NON-INSULIN-DEPENDENT) DIABETES AND IN HYPERTENSIVE NON-DIABETICS

The aim of our study was to compare the effect of captopril - the angi otensin-converting enzyme inhibitor, nifedipine - the calcium antagoni st, and prazosin - the alpha blocker, on the secretory function of pan creatic beta-cells in hypertensive patients with NIDDM and with normal glucose tolerance. The effect of a 2-week treatment with nifedipine, captopril and prazosin upon glycaemia, serum insulin (IRI) and C-pepti de (CP) following oral and intravenous glucose load were investigated in three groups, each including 10 non-diabetic patients with essentia l hypertension (h) and 10 hypertensive type 2 (non-insulin-dependent) diabetics (h + d), aged 32-63 years. Nifedipine produced increase in g lycaemia in the oral test in both groups. In the (h) group, but not in the (h + d) group, the drug caused reduction of the glucose-dependent increases in serum IRI and CP, more marked with respect to CP, as exp ressed by the decrease in the molar serum CP/IRI ratio. These results indicate that in non-diabetic patients, nifedipine reduces the early r esponse of beta-cells to glucose, but this effect is partly compensate d by a decreased insulin uptake by the liver. In patients with type 2 diabetes, this phenomenon does not become manifest because of absence or reduction in the early glucose-dependent insulin release. After cap topril, lower values of glycaemia and serum IRI and CP were observed i n both groups suggesting an improvement of insulin sensitivity. In con clusion, nifedipine has a small influence, and captopril and prazosin are devoided of any influence on the secretory function of pancreatic beta-cells. These drugs may be recommended for the treatment of hypert ension in patients with type 2 (non-insulin-dependent) diabetes.