Photoperiod-dependent modulation of anti-Müllerian hormone in female Siberian hamsters, Phodopus sungorus

Abstract

Fertility and fecundity decline with advancing age in female mammals, but reproductive aging was decelerated in Siberian hamsters (Phodopus sungorus) raised in a short-day (SD) photoperiod. Litter success was significantly improved in older hamsters when reared in SD and the number of primordial follicles was twice that of females held in long days (LD). Because anti-Mü llerian hormone (AMH) appears to inhibit the recruitment of primordial follicles in mice, we sought to determine whether the expression patterns of AMH differ in the ovaries and serum of hamsters raised in SD versus LD. Ovaries of SD female hamsters are characterized by a paucity of follicular development beyond the secondary stage and are endowed with an abundance of large eosinophilic cells, which may derive from granulosa cells of oocyte-depleted follicles. In ovaries from 10-week-old SD hamsters, we found that the so-called 'hypertrophied granulosa cells' were immunoreactive for AMH, as were granulosa cells within healthy-appearing primary and secondary follicles. Conversely, ovaries from age-matched LD animals lack the highly eosinophilic cells present in SD ovaries. Therefore, AMH staining in LD was limited to primary and secondary follicles that are comparable in number to those found in SD ovaries. The substantially greater AMH expression in SD ovaries probably reflects the abundance of hypertrophied granulosa cells in SD ovaries and their relative absence in LD ovaries. The modulation of ovarian AMH by day length is a strong mechanistic candidate for the preservation of primordial follicles in female hamsters raised in a SD photoperiod. Reproduction (2008) 135 335-342

Photoperiod-gonadotropin mismatches induced by treatment with acyline or FSH in Siberian hamsters: impacts on ovarian structure and function

“…Lastly, as described previously, ovarian AMH protein concentrations are threefold higher in SD than in LD hamsters, likely due to the broader distribution of AMH-expressing cells (Kabithe & Place 2008). Previous studies have shown that AMH reduces follicle sensitivity to FSH via reductions in FSH receptor expression in granulosa cells and the inhibition of FSH-stimulated aromatase activity (Pellatt et al 2007).…”

“…Interestingly, although high concentrations of AMH immunoreactive HGCs were observed in the ovaries of SD controls, no differences in Amh mRNA were observed among any of the groups. Western blots have shown that AMH protein levels were threefold higher in SD ovaries compared with LD ovaries at 10 weeks of age (Kabithe & Place et al 2008). However, this study is the first to examine SD-induced changes in Amh mRNA.…”

“…In female Siberian hamsters, exposure to SD before the onset of puberty results in the inhibition of reproductive development and numerous structural and functional differences within the ovary (Ebling 1994, van den Hurk et al 2002, Place et al 2004, Timonin et al 2006, Kabithe & Place 2008. Our goal was to elucidate the Figure 6 MeanGS.E.M.…”

“…These SD-induced differences include reduced ovarian mass, greater numbers of primordial follicles, and an abundance of hypertrophied granulosa cells (HGCs), which surround atretic oocytes (Schlatt et al 1993, van den Hurk et al 2002, Place et al 2004. Whereas oocyte atresia also occurs in the ovaries of LD females, it is not accompanied by the hypertrophy of surrounding granulosa cells (Kabithe & Place 2008). More importantly, HGCs within the SD ovary are immunoreactive for antiMüllerian hormone (AMH), and the abundance of HGCs in SD ovaries likely explains the threefold higher levels of AMH in SD compared with LD ovaries.…”

“…More importantly, HGCs within the SD ovary are immunoreactive for antiMüllerian hormone (AMH), and the abundance of HGCs in SD ovaries likely explains the threefold higher levels of AMH in SD compared with LD ovaries. The broad distribution and abundance of AMH-positive HGCs have been purported to be the mechanism underlying the greater numbers of primordial follicles in SD-reared hamsters (Kabithe & Place 2008), as AMH has been shown to inhibit primordial follicle activation as a result of paracrine effects (Durlinger et al 1999(Durlinger et al , 2002.…”