[Case of intrathoracic pheochromocytoma occurring 9 years after resection of intraabdominal paraaortic pheochromocytoma: effect of metoclopramide and sulpiride on catecholamine secretion in vitro].

A 29-year-old female who had undergone resection of an abdominal paraaortic pheochromocytoma weighing 33 g at the age of 20 had had severe headaches, hypertension and hyperhidrosis 3 years prior to the surgery. Postoperatively, her symptoms completely disappeared and urinary catecholamines were normalized. She was well and had married and had had 2 children. She was admitted to our hospital on August 22, 1982, for further evaluation of hypertension (154/100), which had been diagnosed 2 months previously. Endocrinological studies confirming the presence of a pheochromocytoma were as follows: 1) Plasma noradrenaline level was significantly elevated to 1750 pg/ml. 2) Urinary catecholamine and their metabolites (Metanephrines and VMA) were markedly elevated. Her blood pressure was borderline hypertension and its diurnal rhythm was lost. Her blood pressure decreased to normal values after the oral administration of labetalol (100 mg). Plasma noradrenaline level was still high at 180 minutes after the oral administration of clonidine (150 micrograms). Hypertensive response to insulin-induced hypoglycemia (regular insulin 0.1 u/kg i.v.) was observed, but blood pressure returned to normal after the infusion of glucose alone. Hypertensive response to both metoclopramide (5 mg i.v.) and sulpiride (50 mg per os) was observed accompanying the significant elevation of plasma noradrenaline. Computed tomography and ultrasonography revealed a tumor localized between the aorta and the vena cava inferior. Selective venous sampling also revealed an intrathoracic pheochromocytoma. On October 8, 1982, a 28 g mass was removed from the mediastinum just above the diaphragma. Histologically, it was typical of a pheochromocytoma. Electron microscopy showed large polygonal cells with numerous large secretory granules characteristic of noradrenaline-granules. Postoperative blood pressure was normal, but repeated measurements of plasma and urinary catecholamines were still slightly high. We, therefore, followed her case carefully at our out-patient clinic. In order to clarify the mechanism of catecholamine release by metoclopramide and sulpiride, tissue cultures of removed pheochromocytoma with and without these drugs were carried out. The in vitro studies revealed that metoclopramide released noradrenaline eight-fold and sulpiride 13-fold as compared with noradrenaline in a control medium. We concluded that both drugs stimulated catecholamine secretion directly from the tumor and thus, careless administration of these drugs should be avoided when pheochromocytoma was suspected, large or small. Finally, the rate of tumor growth seemed to be very slow because it took 9 years to ach