Immunohistochemical localization of Met-enkephalin, Met-enkephalin-Arg6-Gly7-Leu8, Met-enkephalin-Arg6-Phe7 and Leu-enkephalin in human adrenal medulla and pheochromocytomas.

Immunohistochemical localization of Met-enkephalin, Met-enkephalin-Arg6-Gly7-Leu8, Met-enkephalin-Arg6-Phe7 and Leu-enkephalin was studied in human adrenal medulla and pheochromocytomas at the light and electron microscopic levels. Both adrenal medulla and pheochromocytomas (4 adrenal, 1 extra-adrenal) showed scattered or clustered cells which contained all of the above peptides and suggested the production of proenkephalin A. The presence of these peptides predominantly in the secretory granules suggested that proenkephalin A is processed to final products mainly in the secretory granules. The localization of Met-enkephalin-Arg6-Gly7-Leu8 and Met-enkephalin-Arg6-Phe7 in cisternae of rough endoplasmic reticula indicated their actual production in pheochromocytomas.