Renal and systemic hemodynamics in sustained essential hypertension.

Cardiac output (CO), renal blood flow (RBF), calf blood flow (CBF), and hepatic blood flow (HBF), glomerular filtration rate (GFR), and dopamine beta hydroxylase (D beta H) activity were studied in 198 men (67 normotensive controls and 131 hypertensive patients) of the same age with sustained uncomplicated essential hypertension. In the hypertensive men, the RBF and the RBF/CO ratio were significantly decreased (p less than 0.001). The RBF and RBF/CO ratio were negatively correlated with age (p less than 0.01), blood pressure (p less than 0.01), and D beta H activity (p less than 0.01). None of these relationships were observed with CBF and HBF. The observed decreases in RBF and the RBF/CO ratio in hypertensive men were reversed after administration of clonidine and alpha-methyldopa (p less than 0.01), but not after administration of propranolol. The study provides evidence that the reduction of renal perfusion in essential hypertension is partly reversible and related to an abnormality in the adrenergic system control.

Relationship between renin and extracellular fluid volume in normotensive and hypertensive subjects.

Plasma renin activity and extracellular fluid volume were determined in 34 normotensive and in 35 sustained essential hypertensive patients with normal renal function, balanced sodium intake and urinary output. In normotensives, plasma renin activity was negatively correlated to extracellular fluid volume (r = 0.54; p = 0.001). The 95% confidence limits of the normotensive curve was used as nomogram to classify the hypertensive patients into two groups: those (23 cases) that fell within the limits of the normal curve (group I) and those (12 cases) that were below these limits (group II). In comparison with group I, group II was characterized by: (i) similar values for age, blood pressure, inulin clearance and extracellular fluid volume and (ii) significantly but lower values (p less than 0.001) for plasma renin activity with maintenance of the relationship between extracellular fluid volume and renin. The study strongly suggests that (i) the hypertensives of group I had no abnormal regulation of the renin-angiotensin system in comparison with the control subjects and (ii) the hypertensives of group II had an extracellular fluid volume-renin relationship set for lower values of renin.

Aldosterone in sustained essential hypertension.

Plasma aldosterone (PA), plasma renin activity (PRA), extracellular fluid volume (EFV) and hepatic blood flow were measured in forty-four patients with sustained essential hypertension and compared with forty-two normotensive controls of same age and sex. All patient had inulin clearances within the normal range and balanced sodium intake and urinary output. In hypertensives, PA, PRA, EFV and hepatic blood flow were within normal ranges; the log-ratio PA:PRA was significantly elevated (P less than 0.001). In normotensives, a negative relationship was observed between PA and EFV (r=-0.55; P less than 0.001) while a positive relationship was observed between PA and PRA (=+0.70; P less than 0.001). In hypertensives, the two relationships were disrupted or less significant: for a given value of EFV, PA was more elevated in hypertensives than in normotensives; for a given value of PRA, PA was more evaluated in hypertensives than in normotensives. The results could not be explained on the basis of a disturbance in hepatic blood flow and/or in the metabolic clearance rate of aldosterone. The study provided evidence that, in patients with sustained essential hypertension and equilibrated sodium balance, there is an excess of plasma aldosterone relative to the levels of extracellular fluid volume and plasma renin activity. The excess of probably related to an abnormality in the adrenal secretion.