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Ann D Nguyen, Samantha M Mapes, C Jo Corbin and Alan J Conley

Human adrenarche is associated with the establishment of a functional zona reticularis (ZR) and increasing secretion of dehydroepiandrosterone (DHEA) in sulfated form (DS). Like most non-human primates, rhesus macaques are not believed to undergo adrenarche, though they clearly establish a functional ZR after birth. However, the origins of the rhesus ZR are not well defined. Therefore, we investigated the zonal development, steroidogenic enzyme expression and morphology of rhesus adrenals from 1 day to 14 months of age. Immunohistochemistry was conducted to determine expression profiles of the steroidogenic enzymes 17α-hydroxylase/17,20-lyase cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17A1), cytochrome P450, family 21, subfamily A, polypeptide 2 (CYP21A2), hydroxy-Δ-5-steroid dehydrogenase, 3β- and steroid Δ-isomerase 2 (HSD3B2), the redox partner NADPH-cytochrome P450 oxidoreductase (CPR), as well as the accessory protein cytochrome b5 (b5), a marker of the primate ZR. The rhesus ZR is mature by 3 months of age based on differentiation of the innermost zone that lacks HSD3B2, but exhibits increased b5 expression during this period. Further, the ZR develops in neonates from a previously described dense band of cells which we show expresses b5, CYP17A1, CPR, and CYP21A2 throughout maturation. The fetal zone (FZ) is distinguished from the ZR by its lack of CYP21A2, and ZR development proceeded as the FZ regressed with two important implications: neither FZ regression nor ZR maturation can be monitored independently by circulating adrenal androgens, and these events must be induced by different factors in rhesus, and likely humans. Collectively these data demonstrate that ZR development begins before birth in the rhesus, proceeding concomitantly with FZ regression post-natally, suggesting that rhesus experiences morphological adrenarche during the first three months of life.

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Renata C Uliani, Alan J Conley, C Jo Corbin, Aimê M Friso, Luciana F S Maciel and Marco A Alvarenga

Anti-Müllerian hormone (AMH) is used as a marker of follicle population numbers and potential fertility in several species including horses but limited data exist across the lifespan. No one has decreased ovarian reserve experimentally to investigate whether a corresponding, quantitative decrease in AMH results. Concentrations of AMH across the lifespan were compiled from 1101 equine females sampled from birth to >33 years of age. Young and old mares (averaging 6 and 19 years) were hemi-ovariectomized and circulating AMH was assessed before and daily thereafter for 15 days. The remaining ovary was removed later and blood was drawn again before and after this second surgery for AMH determination. Polynomial regression analysis and analysis of mares grouped by 5-year intervals of age demonstrated AMH concentrations to be higher in mares aged 5–10 and 10–15 years than 0–5 years of age and lower in mares after 20 years of age. There was high variability in AMH concentrations among neonatal fillies, some of which had concentrations typical of males. Hemi-ovariectomy was followed by a decrease of AMH, almost exactly halving concentrations in intact mares. Concentrations of AMH had returned to intact levels in old mares before complete ovariectomy, as if exhibiting ovarian compensatory hypertrophy, but recovery of AMH was not evident in young mares. AMH may reflect ovarian senescence in mares after 20 years of age but is too variable to do so in the first two decades of life. The ovarian endocrine response to hemi-ovariectomy in mares appears to change with age.