Schirman-Hildesheim Tamar D, Ben-Aroya Nurit, Koch Yitzhak
Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel.
Mol Cell Endocrinol. 2006 Jun 27;252(1-2):120-5. doi: 10.1016/j.mce.2006.03.010. Epub 2006 May 2.
We recently described patterns of GnRH and GnRH receptor (GnRH-R) expression in the hypothalamus, pituitary and ovary throughout the rat estrus cycle. Here, we wished to distinguish between regulatory effects of ovarian factors and underlying circadian rhythmicity. We quantified GnRH and GnRH-R mRNA in the pituitary and hypothalamus of long-term ovariectomized (OVX) rats, at different times of day, using real-time PCR. Furthermore, we expanded our previous study of hypothalamic and pituitary GnRH and GnRH-R expression in intact rats by including more time points throughout the estrus cycle. We found different daily patterns of GnRH and GnRH-R expression in intact versus OVX rats, in both tissues. In the hypothalamus of OVX rats, GnRH mRNA peaked at 12, 16 and 20 h, whereas in the hypothalamus of intact rats we observed somewhat higher GnRH mRNA concentrations at 19 h on every day of the estrus cycle except proestrus, when the peak occurred at 17 h. In this tissue, GnRH-R fluctuated less significantly and peaked at 16 h in OVX rats. During the estrus cycle, we observed higher levels in the afternoon of each day except on estrus. In OVX rats, pituitary GnRH mRNA rose sharply at 9 h, with low levels thereafter. In these animals, pituitary GnRH-R also peaked at 9h followed by a second rise at 22 h. In intact rats pituitary GnRH was high at noon of diestrus-II and on estrus, whereas GnRH-R mRNA was highest in the evening of diestrus-II. This is the first demonstration of daily GnRH and GnRH-R mRNA expression patterns in castrated animals. The observed daily fluctuations hint at underlying tissue-specific circadian rhythms. Ovarian factors probably modulate these rhythms, yielding the observed estrus cycle patterns.
我们最近描述了整个大鼠发情周期中下丘脑、垂体和卵巢中促性腺激素释放激素（GnRH）和GnRH受体（GnRH-R）的表达模式。在此，我们希望区分卵巢因子的调节作用和潜在的昼夜节律性。我们使用实时PCR在一天中的不同时间对长期卵巢切除（OVX）大鼠的垂体和下丘脑内的GnRH和GnRH-R mRNA进行了定量分析。此外，我们通过在发情周期中纳入更多时间点，扩展了之前对完整大鼠下丘脑和垂体GnRH及GnRH-R表达的研究。我们发现，在完整大鼠和OVX大鼠的这两种组织中，GnRH和GnRH-R的每日表达模式有所不同。在OVX大鼠的下丘脑，GnRH mRNA在12、16和20时达到峰值，而在完整大鼠的下丘脑，除了发情前期峰值出现在17时外，在发情周期的每一天，19时的GnRH mRNA浓度均略高。在该组织中，GnRH-R的波动不太明显，在OVX大鼠中于16时达到峰值。在发情周期中，除发情日外，我们在每天下午观察到较高水平。在OVX大鼠中，垂体GnRH mRNA在9时急剧上升，此后水平较低。在这些动物中，垂体GnRH-R也在9时达到峰值，并在22时出现第二次上升。在完整大鼠中，垂体GnRH在动情后期II的中午和发情期时水平较高，而GnRH-R mRNA在动情后期II的晚上最高。这是首次在去势动物中证明GnRH和GnRH-R mRNA的每日表达模式。观察到的每日波动暗示了潜在的组织特异性昼夜节律。卵巢因子可能调节这些节律，从而产生观察到的发情周期模式。
