1. Fifty-five patients with uncomplicated essential hypertension were admitted to hospital, where 25 of them were treated with propranolol (average daily dose 240 mg) and 30 were left untreated.

2. In all of them renal arteriography was carried out, after which procedure renal plasma flow ([123I]hippuran clearance), cortical blood flow (xenon washout) and renal noradrenaline release were measured.

3. Compared with the untreated hypertensive patients, responders to propranolol (mean blood pressure ≤ 110 mmHg) during treatment showed enhanced cortical blood flow and reduced noradrenaline secretion. Non-responders had reduced cortical flow rates, but increased noradrenaline secretion.

4. Both in the untreated group and in the propranolol-treated group an inverse relationship between arterial noradrenaline concentration and cortical blood flow was found.

5. The results indicate that sympathetic activity may be an important determinant of renal blood flow in hypertension. The effectiveness of propranolol seems to depend upon a reduction in α-adrenergic tone.

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