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Up-regulated NEP and APN activity and down-regulated LPO content in patients with pheochromocytomas

Patients with adrenal medullary pheochromocytoma but not patients with non-functional adrenal tumors have elevated content of enkephalins. APN (aminopeptidase N, CD13) and NEP (enkephalinase, CALLA, CD10) peptidases present on the cells from various tissues including neutrophils, are the main enzymes responsible for degradation of enkephalins in vivo. We have compared the APN and NEP activity of neutrophils from patients with adrenal gland tumors (ten feochromocytomas and twelve non-functional adrenal gland tumors), human tumors of different origin (n=9) and 15 healthy donors. In the same patient we also measured lipid peroxidation (LPO) in the plasma. The diagnosis of each patient was confirmed with endocrinology analysis computed tomography (CT) and/or postoperative histology analysis. NEP activity of neutrophils from patients with pheochromocytomas was up regulated (p=0.001) compared to NEP activity of neutrophils from patients with non-functional adenomas, other tumors or healthy persons. Besides only NEP activity, (but not APN activity or LPO content) in pheochromocytoma patients significantly and consistently decreased 15 days after surgery as compared to level before surgery (n=5). APN activity in pheochromocytoma patients was also up regulated (p=0.01) compared to APN activity in patients with non-functional adenomas, other tumors or healthy persons. Contrary to that LPO was elevated in patients with non functional adenomas and other tumors (p<0.05) and unchanged in pheochromocytomas as compared to healthy persons. Thus, NEP activity might be an additional discriminating parameter in diagnosis of pheochromocytomas.

APN; NEP; LPO; pheochromocytoma

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