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Estradiol exposure alters gonadothropin-releasing hormone (GNRH) induced gonadotrope plasticity




Hartshorn, Cheryl, author
Tobet, Stuart, advisor
Clay, Colin, committee member
Hentges, Shane, committee member
Tjalkens, Ron, committee member

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The reproductive axis is dependent upon communication among the hypothalamus, pituitary and gonads. For successful ovulation, a large increase in circulating estradiol provides positive feedback at both the hypothalamic and pituitary levels to promote an luteinizing hormone (LH) surge. An LH surge is necessary for the final maturation of the pre-ovulatory follicle and ovulation. The cellular and molecular events underlying estradiol’s action(s) upon the anterior pituitary gland, specifically gonadotropes, remain elusive. Recent video microscopy experiments showed that pituitary cells in vitro in slice culture move in response to GnRH [Navratil, et al., 2007]; presumably these cells were gonadotropes. The current study utilized a novel transgenic animal model that has gonadotrope specific fluorescence provided by yellow fluorescent protein (YFP) [Wen et al., 2008]. I sought to determine if 17(3-estradiol (E2) working through either a genomic or non-genomic mechanism affected gonadotrope specific movements in response to GnRH. Consistent with earlier studies [Navratil et al., 2007], application of GnRH [100nM] altered the cytoarchitecture of gonadotropes with observable cell process extensions. Using live video- microscopy, exposure to 10nM E2 for fourteen hours significantly enhanced the ability of gonadotropes to extend processes in response to GnRH compared to short-term exposure of E2 (1.5 hours) or vehicle. There was no demonstrable effect of 1.5 hours of E2 exposure on GnRH-induced process extensions. I hypothesize that the differential effect of short-term versus long-term E2 exposure is due to a genomic mechanism that may underlie the ability of E2 to enhance GnRH induced cellular plasticity. Thus, E2 and GnRH may cooperate to maximize the secretory interface between gonadotropes and the adjacent vasculature during the pre-ovulatory LH surge.


Covers not scanned.
Print version deaccessioned 2022.

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Luteinizing hormone releasing hormone


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