Immunohistochemical localization of catecholamine-synthesizing enzymes in human pheochromocytomas

A total of 17 (10 adrenal and 7 extraadrenal) pheochromocytomas were examined immunohistochemically for the localization of catecholamine-synthesizing enzymes-tyrosine hydroxylase (TH), dopamine β-hydroxylase (DBH), and phenylethanolamine N-methyltransferase (PNMT)-as well as the marker peptides for pheochrornocytomas (i.e., met-enkephalin-arggly-leu [MEAGL]). Normal adult, fetal, and newborn human adrenal medullas were also examined. Six adrenal pheochromocytomas showed immunohistochernically positive staining for PNMT; 5 of these cases demonstrated elevated serum adrenalin levels, This indicated morphofunctional correlation. PNMT-positive cells were mostly positive for TH but did not show co-localization of MEAGL except in 1 case, Absence of co-localization was considered to reflect the physiological condition of the specimen, based on the similar staining in the normal adult adrenal medulla. Primary culture and immunoelectron microscopy suggested the processing and synthesis of adrenalin and MEAGL in the secretory granules.Seven extraadrenal pheochromocytornas were negative for PNMT and suggested the lack of adrenalin synthesis.