Effect of Sodium Loading and Exercise on Renal Haemodynamics and Urinary Sodium Excretion in Young Patients with Essential Hypertension before and during Propranolol Treatment

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Abstract
The effects on renal plasma flow (RPF) and glomerular filtration rate (GFR) of an i.v. Na load and exercise were measured in 14 young patients with essential hypertension before and after 3-4 mo. treatment with propranolol as well as in 10 normotensive control subjects. In the untreated hypertensive patients, RPF and GFR were significantly reduced during Na loading and exercise. After propranolol treatment, RPF and GFR were unaffected by Na loading but decreased during exercise. In the normotensive control group, GFR and RPF were unchanged during Na loading; RPF decreased during exercise, whereas GFR was not significantly reduced. RPF was significantly lower in the untreated hypertensive patients than in the normotensive control subjects during Na loading and excercise. Propranolol treatment induced a significant reduction of BP [blood pressure] and heart rate. RPF and GFR were not altered by propranolol treatment during Na loading. During exercise, however, RPF was significantly lower after treatment than before. Urinary Na excretion during Na loading was significantly higher in the hypertensive patients than in the control subjects and decreased significantly during propranolol treatment. The reason for the abnormal reduction in renal hemodynamics during Na loading in patients with essential hypertension is not clarified, but may possibly be related to functional or structural alterations in the renal vascular bed. The lower RPF during exercise after treatment with propranolol is most likely caused by an inhibition of the cardiac output induced by .beta.-adrenergic blockade. The reduced urinary Na excretion during propranolol treatment may be attributable to the reduction of BP.