Release of Neuropeptide Y from Pheochromocytomas

Abstract

To investigate the release of neuropeptide Y (NPY) from the pheochromocytomas, we studied the relationship between the plasma and tumor tissue immunoreactive (IR) NPY concentrations in 13 patients with pheochromocytoma and measured the IR-NPY concentration in plasma samples obtained by catheter from several veins (jugular veins, superior vena cava, renal veins, adrenal veins and inferior vena cava) in 2 patients with pheochromocytoma. The plasma IR-NPY concentration in 13 patients with pheochromocytoma ranged from 118 to 1460pg/ml and the concentration in 10 of 13 patients with pheochromocytoma was above 290pg/ml (the upper limit of normal range). The tumor tissue IR-NPY ranged from 0.025 to 95.3μg/g wet tissue. Plasma IRNPY was parallel with tumor tissue IR-NPY in 13 cases of pheochromocytoma (r=0.76, P<0.01). The highest concentration of IR-NPY was found in plasma obtained from the drainage vein from a tumor among the plasma samples obtained from several veins in 2 cases of pheochromocytoma. These findings indicate that in patients with pheochromocytoma, NPY is in most cases excessively released from the tumors into the systemic circulation and plasma IRNPY in the periphery is increased.