Childs G V, Unabia G, Miller B T
Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston 77555-0843.
Endocrinology. 1994 Apr;134(4):1943-51. doi: 10.1210/endo.134.4.8137763.
Pituitary cells with GnRH receptors increase over 2-fold during diestrus to reach a peak during the morning of proestrus. This is followed by a rapid fall during the afternoon of proestrus to reach a nadir by estrus. The objective of this study was to learn the identity of the new target cells added during diestrus. This was particularly important in view of recent evidence showing that gonadotropes with LH beta and FSH beta mRNA have GH antigens. Pituitary cells from diestrous and proestrous rats were exposed to biotinylated GnRH (Bio-GnRH) for 10 min. Bio-GnRH was detected by avidin peroxidase, and then the cells were immunolabeled for pituitary hormones. The percentages of cells labeled for Bio-GnRH rose during diestrus from 6.6 +/- 0.8% in the morning to 11.9 +/- 0.7% by evening (mean +/- SD). By the morning of proestrus, the percentages of Bio-GnRH target cells increased further to 16 +/- 0.7%. The percentages of pituitary cells dual labeled for LH beta antigens and Bio-GnRH rose from 4.3 +/- 0.6% to 9% +/- 1% during diestrus and averaged 13 +/- 0.7% by the morning of proestrus. At this time, 90% of cells with LH antigens bound Bio-GnRH. When percentages of pituitary cells with FSH beta antigens and Bio-GnRH-binding sites were analyzed, there was an increase during diestrus from 4 +/- 0.4% to 9.7 +/- 0.7%; a peak level of 14 +/- 0.9% was reached by the morning of proestrus. Bio-GnRH binding was expressed by 86% of FSH cells during this peak. Finally, GH antigens were also detected in GnRH target cells. The percentage of cells dual labeled for Bio-GnRH and GH increased from 4 +/- 0.8% to 8 +/- 1% during diestrus and the morning of proestrus. During the diestrous and proestrous peak periods of expression, Bio-GnRH binding was seen in 32% of GH cells. None of the other pituitary cell types showed significant GnRH binding. These studies showed that most of the new GnRH-receptive cells stem from maturing gonadotropes. Half of the GnRH-receptive cells also contain GH antigens, which correlated with results from previous studies that showed GH antigens in cells with gonadotropin mRNAs. This might reflect expression of gonadotrope functions by a subset of GH cells. Alternatively, the GH antigens may be bound to GH receptors in gonadotropes. This latter possibility may signify a paracrine regulation of gonadotrope function by GH.
具有促性腺激素释放激素（GnRH）受体的垂体细胞在间情期增加超过2倍，并在发情前期的早晨达到峰值。随后在发情前期的下午迅速下降，到发情期降至最低点。本研究的目的是了解在间情期新增的靶细胞的身份。鉴于最近的证据表明，具有促黄体生成素β（LHβ）和促卵泡生成素β（FSHβ）mRNA的促性腺激素细胞有生长激素（GH）抗原，这一点尤为重要。将来自间情期和发情前期大鼠的垂体细胞暴露于生物素化的GnRH（Bio-GnRH）中10分钟。通过抗生物素蛋白过氧化物酶检测Bio-GnRH，然后对细胞进行垂体激素免疫标记。标记Bio-GnRH的细胞百分比在间情期从早晨的6.6±0.8%上升到傍晚的11.9±0.7%（平均值±标准差）。到发情前期的早晨，Bio-GnRH靶细胞的百分比进一步增加到16±0.7%。在间情期，同时标记LHβ抗原和Bio-GnRH的垂体细胞百分比从4.3±0.6%上升到9±1%，到发情前期的早晨平均为13±0.7%。此时，90%具有LH抗原的细胞结合了Bio-GnRH。当分析具有FSHβ抗原和Bio-GnRH结合位点的垂体细胞百分比时，在间情期从4±0.4%增加到9.7±0.7%；到发情前期的早晨达到峰值水平14±0.9%。在这个峰值期间，86%的FSH细胞表达Bio-GnRH结合。最后，在GnRH靶细胞中也检测到了GH抗原。在间情期和发情前期的早晨标记Bio-GnRH和GH的细胞百分比从4±0.8%增加到8±1%。在间情期和发情前期的表达高峰期，32%的GH细胞可见Bio-GnRH结合。其他垂体细胞类型均未显示出明显的GnRH结合。这些研究表明，大多数新的GnRH受体细胞来源于成熟的促性腺激素细胞。一半的GnRH受体细胞也含有GH抗原，这与先前显示促性腺激素mRNA细胞中有GH抗原的研究结果相关。这可能反映了一部分GH细胞表达促性腺激素功能。或者，GH抗原可能与促性腺激素细胞中的GH受体结合。后一种可能性可能意味着GH对促性腺激素细胞功能的旁分泌调节。
