1. Concentrations of noradrenaline and adrenaline from peripheral venous plasma were measured after 60 min of supine rest in 55 patients on chronic haemodialysis (including six anephric patients) and in 18 normal subjects. In the patients, plasma catecholamine measurements were related to concurrent measurements of blood pressure, pulse rate, plasma renin activity, plasma angiotension II, blood volume and sulphate space.
2. Mean resting peripheral venous plasma noradrenaline concentration was higher by almost twofold, but mean resting plasma adrenaline concentration was lower, in the 49 non-nephrectomized patients than in the normal subjects. In the six anephric patients, resting peripheral venous plasma noradrenaline concentrations were similar to those of normal subjects.
3. Mean resting plasma noradrenaline concentrations in peripheral venous blood were similar in normotensive and hypertensive non-nephrectomized patients; mean plasma adrenaline concentration was higher in the hypertensive patients. A positive correlation was found between plasma adrenaline and plasma renin activity but not between plasma noradrenaline and plasma renin activity.
4. Resting concentrations of both catecholamines were positively correlated with resting pulse rate and inversely related to blood volume.
5. After renal transplantation resting peripheral venous plasma noradrenaline concentrations were normal in eight patients in whom high values had been recorded whilst on chronic haemodialysis.
6. In response to 40° of head-up tilt, plasma noradrenaline increased significantly in six non-nephrectomized patients, whether sodium replete or depleted, and the changes observed in both these states were similar to those of 14 normal subjects studied on a normal diet.
7. Diastolic blood pressure increased on standing in the majority (41/55) of patients: in only four patients was there a fall in diastolic pressure of more than 5 mmHg in the erect position and in two of these blood volumes were low.
8. The cause of increased peripheral plasma noradrenaline concentrations in haemodialysis patients is uncertain.