Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, S2-072 Schurman Hall, Ithaca, New York 14853, USA.
Reproduction. 2012 Nov;144(5):603-16. doi: 10.1530/REP-12-0155. Epub 2012 Aug 30.
Many seasonal breeders time their reproductive efforts to specific times of the year to ensure adequate resources for the production and care of young. For long-day (LD) breeders, females born before the summer solstice (LDs) reach sexual maturity quickly and often breed that same year, whereas females born after the summer solstice (short days (SDs)) may delay reproductive development to the following spring when environmental conditions are favorable for reproduction. In Siberian hamsters, development in SD is associated with structural and functional differences in the ovary compared with females held in LD, including a greater number of primordial follicles and an abundance of hypertrophied granulosa cells (HGCs), which are immunoreactive for anti-Müllerian hormone. The goal of this study was to determine whether SD-induced gonadotropin suppression is responsible for these phenotypic differences. Gonadotropin levels were suppressed in LD hamsters using the GNRH antagonist acyline. Conversely, to determine whether the SD ovarian phenotype is completely reversed by gonadotropin stimulation, recombinant human FSH (rhFSH) was administered. Our treatments were successful in mimicking FSH concentrations of the opposite photoperiod, but they did not produce a comparable change in the ovarian phenotype. Most notable was the lack of HGCs in the ovaries of acyline-treated LD females. Similarly, HGCs were maintained in the ovaries of SD females treated with rhFSH. Our data suggest that gonadotropins alone do not account for the SD ovarian phenotype. Future studies will determine whether SD-induced changes in other factors underlie these phenotypic changes.
许多季节性繁殖者会将繁殖努力安排在一年中的特定时间，以确保为幼崽的生产和照顾提供足够的资源。对于长日照（LD）繁殖者，夏至前出生的雌性（LDs）会迅速达到性成熟，并且通常会在当年繁殖，而夏至后出生的雌性（短日照（SDs））可能会延迟繁殖发育，直到次年春天环境条件有利于繁殖时再进行。在西伯利亚仓鼠中，与在 LD 中饲养的雌性相比，SD 中的发育与卵巢的结构和功能差异有关，包括更多的原始卵泡和大量肥大的颗粒细胞（HGCs），这些细胞对抗苗勒管激素呈免疫反应。本研究的目的是确定 SD 诱导的促性腺激素抑制是否是这些表型差异的原因。使用 GnRH 拮抗剂 acyline 抑制 LD 仓鼠中的促性腺激素水平。相反，为了确定 SD 卵巢表型是否完全被促性腺激素刺激逆转，我们给予重组人 FSH（rhFSH）。我们的处理成功地模拟了相反光周期的 FSH 浓度，但它们并没有使卵巢表型产生类似的变化。最值得注意的是，acyline 处理的 LD 雌性的卵巢中缺乏 HGCs。同样，rhFSH 处理的 SD 雌性的卵巢中维持着 HGCs。我们的数据表明，促性腺激素本身并不能解释 SD 卵巢表型。未来的研究将确定 SD 诱导的其他因素变化是否是这些表型变化的基础。
