EFFECTS OF NITRENDIPINE ON BLOOD-PRESSURE, RENIN-ANGIOTENSIN-SYSTEM AND ATRIAL-NATRIURETIC-PEPTIDE IN HYPERTENSIVE TYPE-I DIABETIC-PATIENTS

In this study, the effects of a six week treatment with the calcium channel blocking agent nitrendipine were assessed in 20 hypertensive type I diabetic patients who received a single oral dose of 20 mg daily. Plasma concentrations of atrial natriuretic peptide (ANP), plasma renin activity (PRA) and active renin, aldosterone, glycosylated hemoglobin (HbA1) and fructosamines were determined at the beginning and the end of the study. Interactions of these endocrine parameters with blood pressure behaviour were analyzed by a correlation matrix. In response to the drug treatment, the blood pressure was significantly lowered from 158.0/97.2 to 145.7/88.2 mmHg. The plasma concentrations of ANP were also significantly reduced from 106.8 to 89.7 pg/ml. There were no changes in serum aldosterone, while PRA and active renin exhibited a significant increase following the six week treatment. HbA1 and fructosamines remained unaltered. There were no significant correlations for ANP and blood pressure values, as well as for ANP and PRA or aldosterone. We did find, however, a significant correlation of the ANP values with the difference of the systolic blood pressure levels pre- and post-treatment. These data fully confirm the blood pressure lowering properties of this calcium channel blocker and its possible interference with steroidogenesis, since the effects of increased PRA on aldosterone secretion were clearly blunted. The lowering of plasma ANP levels may represent a decreased ANP secretion due to calcium channel blockade or might also be due to the natriuretic effects of nitrendipine, thus allowing ANP levels to decline as a function of lessened sodium retention. Moreover, our data clearly indicate that pre-treatment ANP levels may represent a predictive criterion of the therapeutic efficacy of nitrendipine.