Relation between dopamine secretion and saltsensitivity in essential hypertension

Abstract

The study was designed to explore the mechanism of dopamine secretion related to blood pressure in patients with essential hypertension. The 19 patients with essential hypertension were administered to first 153 mEq of sodium and 70 mEq of potassium diet, next 51 mEq of sodium and finally 340 mEq of sodium for every one week. The patients whose mean blood pressure elevated 10 mmHg or more on the high-sodium loading and depleted 10 mmHg or more on the low-sodium loading were classified as A-, and depleted 10 mmHg or more on the high-sodium loading and elevated 10 mmHg or more on the low-sodium loading as B- and the other patients as C-group. The hypertensive patients were also classified to low- (below 1.0 ng/ml/h), normal- (from 1.0 to 6.0 ng/ml/h) and high- (above 6.0 ng/ml/h) renin groups from the results of plasma renin activity (PRA) obtained after an intravenous injection of furosemide (1 mg/kg) followed by 2-hour ambulation. PRA, plasma aldosterone concentration (PAC), plasma epinephrine concentration (PE), plasma norepinephrine concentration (PNE), plasma dopamine concentration (PDC), circulating plasma volume, body weight, hematocrit and pulse rate were measured at 8 a.m. after sodium loading for 8-days. The patients with essential hypertension were classified into 6 of A- and 2 of B- and 11 of C-groups with the maneuver of sodium loading. The A-group contained 5 patients with low-renin. The circulating plasma volume was relatively large (44.7 +/- 4.8 ml/kg) and markedly increased on the high-sodium loading in 6 patients of A-group. The increment of body weight was higher in A-group than the other groups on the high-sodium loading. In the 2 patients of B-group, hematocrit and pulse rate increased on the low-sodium and decreased on the high-sodium loading, and the variability were larger than the other groups. In the A-group, PRA was significantly low (0.5 +/- 0.4 ng/ml/h) and increased on the low-sodium loading and decreased on the high-sodium loading, and the variability of PRA was lesser than the other groups. In the A-group, PAC was within normal range (5.4 +/- 2.8 ng/dl) and the variation of PAC paralleled with the change of PRA, but the variability of PAC was remarkably low. PE and PNE were unchanged in the A- and the C-groups, but the significant high values were observed in the B-group on the high-sodium loading.