Gender and gonadal status differences in zona reticularis expression in marmoset monkey adrenals: Cytochrome b5 localization with respect to cytochrome P450 17,20-lyase activity.

Neonatal marmosets express an adrenal fetal zone comparable to humans. While adult males fail to express a functional ZR, with barely detectable blood DHEA levels, females produce higher levels of DHEA than males in adulthood. We investigated the presence of a putative functional ZR in adult female marmosets. In contrast to males, immunohistochemical analysis showed the ZR marker cytochrome b5 was elevated in the innermost zone in cycling females (compared to testis-intact males), further elevated in the adrenals from anovulatory females, and substantially elevated and continuous in ovariectomized females. As a functional test in vivo, following overnight dexamethasone treatment, cycling and anovulatory females showed higher levels of DHEA relative to males, but DHEA failed to increase in response to ACTH. In direct contrast, while ovariectomized females exhibited lower initial DHEA levels, clear increases were detectable after ACTH administration (p<0.05), suggesting an adrenal origin. The apparent differences in cytochrome b5 expression between groups were also further verified by Western blotting of adrenal microsomes, and compared to 17,20-lyase activity; the two parameters were positively correlated (p<0.01) across multiple treatment groups. We conclude that the cycling female marmoset expresses a rudimentary ZR with at least a capacity for DHEA production that becomes significantly ACTH-responsive after anovulation. Expression of cytochrome b5 in this region may be directly or indirectly controlled by gonadal function, and is, at least in part, a critical determinant in the development of an adrenal ZR that is more defined and significantly ACTH-responsive.