Immunohistochemical study of cytochrome b5 in human adrenal gland and in adrenocortical adenomas from patients with Cushing's syndrome

Abstract

Cytochrome b5, a component of the electron transfer system increases the relative activity of 17,20-lyase to 17α-hydroxylase of P450c17 in vitro. In the present study, immunohistochemical analysis of cytochrome b5 was performed in the human adrenal gland and in adrenocortical adenomas from patients with Cushing's syndrome. In the human adrenal gland, cytocrome b5 was stained in all three adrenocortical layers but the staining was most remarkable in the zona reticularis. All of the adenomas were composed mainly of compact cells, which exhibited immunoreactive staining for cytochrome b5 as well as for P450c17 and 3β-hydroxysteroid dehydrogenase (3β-HSD). The distribution of b5 in the adenomas was correlated with that of P450c17 rather than with that of 3β-HSD. The immunoreactive staining for cytochrome b5 appeared to be more prominent in the two adenomas that produced relatively high concentrations of adrenal androgens than in adenomas that produced low concentrations of adrenal androgens. These results immunohistochemically support the functional association of b5 with androgen production through interaction with P450c17 and the previous finding that higher concentrations of cytochrome b5 are associated with greater production of adrenal androgens in adrenocortical adenomas from patients with Cushing's syndrome.