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

Abstract

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.

Plasticity of the zona reticularis in the adult marmoset adrenal cortex: voyages of discovery in the New World

“…The reversibility of social status makes the model advantageous for researchers as the formation of social groups and experiments on behavior and in vivo physiologic responses are not terminal. In view of this phenomenon, and indeed in light of Levine's previous studies of elevated DS in female marmosets of 18 months or older (Levine et al 1982), similar studies to those in males were repeated in females by Pattison et al (2007), with surprising results. Immunohistochemical analysis showed that the ZR marker CYTB5 was elevated in the innermost zone in ovary-intact, regularly cycling adult females compared with testis-intact adult males, was further elevated in adrenals from ovary-intact, anovulatory (socially subordinate) adult females, and was substantially elevated with solid/continuous staining in the innermost adrenocortical zone in ovariectomized adult females (Pattison et al 2007; summarized in part in Fig.…”

“…Our own data (Pattison et al 2005(Pattison et al , 2007 suggest that in the marmoset, expression of CYTB5 may well contribute to DHEA production in vivo. It is therefore of considerable relevance that the amino acids at position 347 and 358 in human that are important for P450c17 interactions with CYTB5 are highly conserved in both marmosets and rhesus monkeys.…”

“…The apparent differences in CYTB5 expression between groups were further verified by western blotting of adrenal microsomes, and were compared with 17,20-lyase activity in the same preparations; the two parameters were positively correlated to a high degree of significance (P!0 . 01) across multiple treatment groups (Pattison et al 2007). This correlation is particularly important since it provides the first functional data indicating that while ZR expression of CYTB5 clearly differs between adult male and adult female marmosets, and even differs with the social/physiologic state of adult females (i.e.…”

“…socially dominant/cycling compared with subordinate/ anovulatory compared with ovariectomized), ZR 17,20-lyase activity relates directly to the level of CYTB5 expression in the adrenal ZR regardless of sex or physiologic state of females. It was concluded by Pattison et al (2007) that ovary-intact, regularly cycling adult female marmosets express a rudimentary ZR with at least a capacity for DHEA production that may well depend on the level of CYTB5 expression. The fact that expression of CYTB5 increased so dramatically on ovariectomy was also the first direct finding that, in marmosets at least, expression of ZR CYTB5 may be directly or indirectly suppressed by gonadal function.…”

“…Given that this is also the first such study in New World primates, it is all the more important to characterize both P450c17 hydroxylase and 17,20-lyase function and the role of CYTB5 in selective control of 17,20-lyase activity. While a deficiency of delta-4-lyase activity (activity on 17-hydroxyprogesterone) has been inferred in studies of marmoset adrenal microsomes (Pattison et al 2005(Pattison et al , 2007, definitive proof of this important regulatory step was still lacking. Perhaps, the biggest limitation of all was that the primary amino acid sequence was unknown for this New World primate, until very recently.…”