Renal and hemodynamic responses to bumetanide in hypertension: effects of nitrendipine

The effects of a calcium antagonist on the response to a loop diuretic were tested in eight hypertensive patients while they received 120 mmol.24 hr-1 of dietary Na. Nitrendipine (N; 20 mg) or placebo (P) was administered twice daily for five days and bumetanide (B; 1 mg, i.v.) for the last three days of each period. Cardiac index (CI) was measured during tilt. B alone significantly (P less than 0.05; N = 7) reduced CI and increased total peripheral resistance; N prevented these effects of B. Neither drug altered BP consistently. Although three days of B increased plasma renin activity (PRA) during P and N, it increased plasma aldosterone (PAldo) only during P (P, 4.4 +/- 1.3 to 7.6 +/- 1.0; P less than 0.05, N, 5.7 +/- 1.3 to 6.0 +/- 1.3; pg.liter-1; NS). B increased Na excretion without changing GFR or RPF; this was followed by 18 hours of decreased renal Na excretion. These actions were unchanged by N. N did not change the cumulative excretion of B (P, 268 +/- 35 vs. N, 217 +/- 21 micrograms) or the relationship between Na excretion and the log of B excretion. However, Na excretion was increased (P less than 0.05) by 40 to 60% in the six hour period following the first two doses of N. Therefore, the cumulative Na balance was more negative during five days of N (P, -47 +/- 17 vs. N, -108 +/- 24 mmol; P less than 0.05). The effect of N and B on Na balance were independent.(ABSTRACT TRUNCATED AT 250 WORDS)