Plasma catecholamines and dopamine-beta-hydroxylase activity in chronic renal failure

Abstract

Plasma and urinary catecholamines (CA) and plasma dopamine β-hydroxylase (DBH) activity were studied serially in 17 hypertensive patients with chronic renal failure (CRF) and in 15 age-matched patients with benign essential hypertension (EH). Resting levels of plasma epinephrine (E) plus norepinephrine (NE) in CRF patients were significantly greater than those in EH patients ( P < 0.05), whereas plasma DBH activities in CRF patients tended to be lower than those in EH patients ( P < 0.1). However, DBH activities were found to be similar for the two groups, when they were expressed in units per litre of blood instead of per litre of plasma. Urinary free E + NE and dopamine were significantly less in CRF than in EH, whereas no significant difference was noted in urinary excretion of conjugated E + NE and vanillylmandelic acid between the two groups. The ratio of conjugated E + NE/free E + NE and of vanillylmandelic acid/free E + NE were significantly greater in CRF than in EH patients ( P < 0.05). Glomerular filtration rate correlated significantly with free E + NE, free and conjugated dopamine, and inversely with the ratio of conjugated E + NE/ free E + NE in the whole subjects. These findings suggest that raised plasma CA concentration associated with the relative enhancement of extraneuronal inactivations may be relevant to the retarded clearance of circulating CA rather than increased CA release in CRF patients. It is likely that many factors unrelated to sympathetic nerve discharge have a considerable influence on both plasma CA concentration and plasma DBH activity in CRF patients, making them unreliable for studying the role of sympathetic nerve activity in these patients.