engleski

Enkephalinase activity in patients with adrenal gland tumors

Introduction. Adrenal gland as a major source of enkephalins on the periphery can be affected by rare adrenal gland tumor, adrenal pheochromocytoma. It has been demonstrated that this tumor contains high concentration of enkephalin-like peptides. The effect of this peptides can be either prolonged or abbreviated by two neutrophil membrane bound enzymes ; aminopeptidase N (APN) and neutral endopeptidase (NEP). We assumed that altered enkephalin level in pheochromocytoma patients (but not in patients with non-functional adenomas or tumors of different origin) might be associated with differently regulated APN and/or NEP activity. Patients and methods. In patients with pheochromocytomas, non-functional adenomas, abdominal tumors of different origin or healthy controls, we measured APN and NEP activity on surface of neutrophils, level of lipid peroxidation (LPO) in plasma and enkephalin concentration in plasma. Catheholamines and vanyllmandelic acid (VMA) were measured in 24-hour urine of pheochromocytoma patients. Results. NEP and APN activity on neutrophils from all pheochromocytoma patients was significantly increased as compared with healthy controls, non-functional adenomas and other abdominal tumors. In all pheochromocytoma patients NEP activity was reduced almost to the control level after surgery. At the same time APN activity was in some patients up- and in others down-regulated. Compared to that, elevated levels of cateholamines and VMA were found after multiple determination in 6 out of 10 pheochromocytoma patients. Conclusion. This study has shown specifically and consistently up-regulated NEP activity on neutrophils from pheochromocytoma patients, and uniformly decreased NEP activity in same patients after surgery. Thus, measuring NEP activity may represent a simple and quick additional tool in diagnosis of pheochromocytomas.

enkephalinase; adrenal gland; tumor

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