Alterations in plasma dopamine-beta-hydroxylase and catecholamine concentrations during surgical removal of pheochromocytoma.

In order to determine the mechanism of release of catecholamines from pheochromocytoma plasma levels of noradrenaline (NA), adrenaline (A), dopamine (DA) and dopamine-beta-hydroxylase (DBH) were measured in 6 patients with pheochromocytoma undergoing surgical treatment. In 4 patients both the DBH activity and plasma catecholamine concentrations rapidly increased during surgical manipulation of the tumor. In the remaining 2 patients dispite increase of plasma catecholamines DBH activity remained unchanged during surgical manipulation of the pheochromocytoma. The present results suggest that a certain fraction of plasma catecholamines in patients with pheochromocytoma is released from the tumor by exocytosis.