Effects of chronic beta-adrenergic blockade on systemic and renal haemodynamic responses to hyperosmotic saline in hypertensive patients

1. Ten patients with essential hypertension received an intravenous load of hyperosmotic saline before and during treatment with propranolol. In seven patients blood pressure was lowered by the drug.

2. In the control period saline infusion induced a sharp rise in cardiac output due to an increase in stroke volume. This pattern was absent during beta-adrenergic blockade. Renal blood flow showed a moderate rise in the control studies; this rise was not reduced during treatment. Natriuresis was reduced by propranolol.

3. Measurements of central blood volume and central venous pressure in five patients revealed that modified responses during beta-adrenergic blockade may be due to a reduced venous return rather than to myocardial depression.

Studies on the mechanism of hypernatriuresis in essential hypertension in relation to measurements of plasma renin concentration, body fluid compartments and renal function

1. In twenty-two patients representing different stages of benign essential hypertension, hyperosmotic saline was administered intravenously. Determinations of intra-arterial pressure, renal plasma flow, glomerular filtration rate and plasma renin concentration were carried out before and, in the majority, also during and after saline infusion. Changes in cardiac output were followed in ten patients. Plasma volume and extracellular volume were determined in the control period only, although haemodilution was assessed by haematocrit readings.

2. Excess of sodium excretion showed a wide range and was related to the patient's age, as well as to a set of parameters reflecting intrarenal pressure patterns; hypernatriuresis consistently occurred in older patients, in whom renal vascular resistance and nitration fraction were elevated and plasma renin was suppressed. It could not be clarified whether hypernatriuresis together with renin suppression were determined by intrarenal pressure relationships or by an independent age-related factor in the hypertensive patient.

3. Excess of sodium excretion was not related to increments in arterial pressure, cardiac output, renal blood flow or glomerular filtration rate.

4. Plasma renin concentration failed to show consistent changes after hyperosmotic saline infusion.

5. It is concluded that natriuresis is not mediated by changes in the activity of the renin-angiotensin system. Hypernatriuresis appears to be a feature of progressive benign hypertension.

Abnormal renal haemodynamics and renin suppression in hypertensive patients

1. Intra-arterial pressure, renal plasma flow and glomerular filtration rate were estimated in thirty-two patients with benign essential hypertension. In twenty cases plasma renin concentrations were also determined. Variability of blood pressure was estimated by automatic indirect pressure recording.

2. There was an even distribution between high and low values of renal vascular resistance and filtration fraction. Variability of blood pressure was inversely related to renal vascular resistance.

3. In five patients plasma renin concentration was found to be abnormally low both in the recumbent and in the 45° tilt position.

4. Plasma renin concentration was related to renal blood flow, renal vascular resistance, filtration fraction and variability of blood pressure.

5. The results suggest that in hypertension renin release is suppressed by an increase in intravascular pressure at the level of the juxtaglomerularcells. The extent of renin suppression seems to be related to the stage of hypertensive disease.