The Effects of Nifedipine and Captopril on Renal Function in Patients with Essential Hypertension

In comparison with a nonspecific vasodilator, sodium nitroprusside (SNP), we intended to deduce the characteristics of nifedipine (NIF) and captopril (CAP) in the treatment of hypertension. Ten patients with essential hypertension were hospitalized and kept on a constant sodium diet (10 g NaCl/day). Renal blood flow (RBF) and glomerular filtration rate (GFR) were measured before and after the respective administration of SNP (0.9 +/- 0.5 mcg/kg/min), NIF (17 +/- 5 mg), and CAP (85 +/- 24 mg). SNP significantly reduced the mean blood pressure (MBP), the renal vascular resistance index (RVRI), urine volume (UV), urinary excretion of sodium (UNaV), and significantly raised active renin concentration (ARC), plasma norepinephrine (NE), and the heart rate (HR). RBF, GFR, and plasma epinephrine (E) were not changed. Compared with SNP, NIF significantly raised RBF, UV, UNaV, and fractional excretion of sodium (FENa) and significantly reduced RVRI. The differences between the increases in ARC, NE, and HR by NIF and those by SNP were not significant. GFR and E were not changed by NIF. Although CAP did not reduce MBP as much as SNP did, the increase in RBF by CAP was significantly greater than that by SNP. Changes in GFR, UV, UNaV, FENa, and E by CAP were not different than those by SNP. CAP increased ARC and did not raise E, NE, and HR. In conclusion, compared with SNP, NIF significantly raised RBF, UV, UNaV, and FENa and significantly reduced RVRI. On the other hand, the renal response to CAP was not very much different from the response to SNP. The characteristics of CAP were the suppressed sympathetic response to the decrease in blood pressure.