[Ultrastructural and immunohistochemical localization of endothelin-1 in nonneoplastic, hyperplastic and neoplastic adrenal gland].

OBJECTIVE

To determine the ET-1 immunoreactivity in human nonneoplastic, hyperplastic and neoplastic adrenal gland ultrastructurally and histologically.

METHODS

Sensitive immunohistochemical technique was used.

RESULTS

The ET-1 immunoreactivity was found in non-neoplastic (100%), adrenal cortical adenoma (100%) and cortical carcinoma (3/10). ET-1 immunoreactivity was regularly seen in the cortex, especially in zona fasciculata and to a varying extent also in the other two zones, but not in the medulla. The immunoreactive material in the cytoplasm was mostly in vacuolar or grain-like structures. Focally, cell membrane also showed immunoreactive staining. Most cortical adenomas displayed numerous immunoreactive cells. The immunoreactivity in the tumor tissue was in the same forms as in normal cortex, but the reactive products were generally few. No obvious differences in immunostaining were seen between the aldosterone- and cortisol-producing adenomas or the non-functioning ones. Three of the ten carcinomas contained immunoreactive cells, but they were few and appeared focally. The ET-1 immunoreactive structures were seen as "dust-like" material. Electronmicroscopical investigation revealed ET-1 immunoreactive products adjacent to the outer surface of the membrane of lipid bodies, in mitochondria, rough endoplasmic reticulum and focally on the cell membrane, but no immunolabelling was seen in the medulla.

CONCLUSIONS

The localization of ET-1 in the endoplasmic reticulum indicates that this peptide is synthesized in the cortical cells. The localization in the membrane of the lipid bodies and in the mitochondria indicates that it may take part in steroid synthesis. The focally immunolabelled cell membranes may depend on ET-1 bond to ET receptors. The difference in immunoreactivity between the benign and the malignant cortical neoplasms may be of diagnostic value.