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  • Author: Alan J Conley x
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J Christina Pattison, David H Abbott, Wendy Saltzman, Alan J Conley and Ian M Bird

Adrenarche in humans occurs at the age of 5–7 years, yet the process by which dehydroepiandrosterone (DHEA) biosynthesis in the adrenal zona reticularis (ZR) increases so dramatically remains as a matter of debate. One suggestion is that increased DHEA production by P450c17 (CYP17A1 as listed in HUGO Database) in the ZR results from a coincident fall in the expression of HSD3B, which would otherwise compete for pregnenolone substrate. Nonetheless, studies of human and rhesus adrenal show that cytochrome b5 (CYTB5) expression increases in the ZR with DHEA biosynthesis, and cloned human and rhesus P450c17 show selective increases in 17,20-lyase activity in the presence of CYTB5. The marmoset, a New World primate, expresses a fetal zone during development which regresses after birth. Adult males, however, do not develop an obvious functional ZR, while females develop a ZR in a manner that depends on their social/gonadal status. In all social and physiologic states, changes in marmoset ZR function relate directly to changes in the expression of CYTB5. Recent cloning and expression of marmoset P450c17 also show that while amino acid sequence homology is in the order of ∼85% of that found in human and rhesus sequences, and basal lyase activity is low compared with rhesus, all previously described amino acids critical to human 17,20-lyase activity are completely conserved. Furthermore, the 17,20-lyase activity of the marmoset P450c17 clone is dramatically increased by addition of CYTB5. We propose that these combined data from the marmoset model provide further compelling evidence that the control of ZR CYTB5 expression is a key determinant of ZR function.

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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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Kimberley D Katleba, Erin L Legacki, Alan J Conley and Trish Berger

Development of the epididymis including blood–epididymal barrier formation is not required until sperm reach the epididymis peripuberally. Regulation of this development in the early postnatal period is largely unknown. The current objectives were to evaluate potential roles of endogenous estrogen and androgen signaling during early development of the corpus epididymidis and to determine the timing of formation of the blood–epididymal barrier in the pig. Effects of endogenous steroids were evaluated using littermates treated with vehicle, an aromatase inhibitor (letrozole) to reduce endogenous estrogens, an estrogen receptor antagonist (fulvestrant) or an androgen receptor antagonist (flutamide). Phosphorylated histone 3 immunohistochemistry was used to identify proliferating epithelial cells. Lanthanum nitrate and electron microscopy were used to analyze formation of the blood barrier in the corpus epididymidis. Reducing endogenous estrogens increased the number of proliferating corpus epithelial cells at 6 and 6.5 weeks of age compared with vehicle-treated boars (P<0.01 and P<0.001 respectively). Blocking androgen receptors did not alter proliferation rate at 6.5 weeks of age. Although barrier formation was similar between 6 and 6.5 weeks of age in vehicle-treated animals, intercellular barriers increased in letrozole-treated littermates at 6.5 weeks of age. Fulvestrant treatment, which should mimic aromatase inhibition for regulation through ESR1 and ESR2 signaling but potentially stimulate endogenous estrogen signaling through the G protein-coupled estrogen receptor (GPER), had the opposite effect on aromatase inhibition. These responses in conjunction with the presence of GPER in the corpus epididymidis suggest early corpus epididymal development is regulated partially by GPER.

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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.