1. In 20 subjects with uncomplicated essential hypertension, 10 of whom were on propranolol treatment, several blood samples were drawn simultaneously from the renal artery and vein after angiographic studies. In these samples we determined concentrations of noradrenaline, active renin, aldosterone and cortisol.
2. Renal blood flow was measured in all patients by Hippuran-clearance and xenon-washout.
3. Despite marked variations in the arteriovenous difference of noradrenaline, it was apparent in both groups that the kidney is able to release noradrenaline.
4. In the propranolol-treated group noradrenaline secretion by the kidney was enhanced when compared with untreated hypertensive patients.