ULTRASTRUCTURAL-LOCALIZATION OF ENDOTHELIN-1 IN NONNEOPLASTIC, HYPERPLASTIC, AND NEOPLASTIC ADRENAL-GLAND

Endothelin (ET)-1 is a 21-amino acid peptide with potent vasopressor a nd vasoconstrictive properties. Biochemical and recent histochemical s tudies have shown that this peptide is present in human adrenal cortex . This study was intended to determine ET-1 immunoreactivity in human adrenal cortex and cortical adenoma, and hyperplasia ultrastructurally . Light microscopical examination confirmed recent findings of ET-1 im munoreactivity in the three cortical zones (but not in the medulla) as well as in cortical adenoma and cortical hyperplasia. The immunoreact ivity in the cortex and adenoma appeared in the cytoplasm in the form of vacuolar structures and grains. Focally, the cell membranes also sh owed immunoreactive staining. Electronmicroscopical investigation reve aled ET-1 immunoreactive products adjacent to the outer surface of the membrane of lipid bodies, in mitochondria and rough endoplasmic retic ulum and focally on the cell membrane, but no immunolabeling was seen in the medulla. The localization of ET-1 in the endoplasmic reticulum indicates that this peptide is synthesized in the cortical cells. Its localization in the membrane of the lipid bodies and in the mitochondr ia suggests that it takes part in synthesis and/or secretion of steroi d hormones. The focally immunolabeled cell membranes may be dependent on ET-1 binding to ET receptors.