Comparative study of plasma dopamine-beta-hydroxylase activities in noradrenaline-secreting and adrenaline-secreting phaeochromocytomae.

1. Circulating dopamine-beta-hydroxylase activities were measured in two hypertensive patients, with a phaeochromocytoma tumour. Tumours were found to differ by their secretory properties, one secreting noradrenaline, the other adrenaline. After removal of the tumour, the plasma dopamine-beta-hydroxylase activities in both patients gradually decreased to reach a stable value in correlation with urinary, excreted catecholamine levels. The only difference was the rate of the plasma enzyme activity decrease. 2. Thus, it appeared that some phaeochromocytomae are able to secrete dopamine-beta-hydroxylase in addition to catecholamines. Therefore, dopamine-beta-hydroxylase activity measurements may be of interest: (1) in determining secretory properties of phaeochromocytoma tumours, and (2) in following the evolution during the postoperative period.