[Plasma dopamine-beta-hydroxylase activity in pheochromocytoma (author's transl)].

In 3 patients with proved pheochromocytoma, circulating catecholamine concentrations, vanillylmandelic acid and total free catecholamine urinary excretion, dopamine-beta-hydroxylase activities in plasma were measured the day before surgery, during the removal of the tumour and postoperatively. Following the removal of the pheochromocytoma, all these parameters declined with a different rate, possibly related to the half-life proper to each molecule. The results showing a decrease in plasma D beta H activities after the removal of the tumors are in good accordance with most authors. The mechanism and the meaning of catecholamines release from non-innervated tumor-cells remain to be elucidated. By considering these three cases, it does not seem that the evolution of D beta H activity after removal of the tumor is dependent upon the fact that the pheochromocytoma releases preferentially either epinephrine or nephinephrine.