DEVELOPMENT OF GONADOTROPE DESENSITIZATION TO GONADOTROPIN-RELEASING-HORMONE (GNRH) AND RECOVERY ARE NOT COUPLED TO INOSITOL PHOSPHATE PRODUCTION OR GNRH RECEPTOR NUMBER
DEVELOPMENT OF GONADOTROPE DESENSITIZATION TO GONADOTROPIN-RELEASING-HORMONE (GNRH) AND RECOVERY ARE NOT COUPLED TO INOSITOL PHOSPHATE PRODUCTION OR GNRH RECEPTOR NUMBER
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DOI：
10.1210/en.131.6.2681
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发表时间：
1992-12-01
期刊：
影响因子：
4.8
通讯作者：
CONN, PM
中科院分区：
文献类型：
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作者：
HAWES, BE;CONN, PM
初始GnRH预处理后（10 nm，5 h），随后GnRH刺激的促性腺细胞LH释放减少（1 μ M GnRH在最初用单独培养基预处理的细胞中刺激释放36.4 +/-1.4%总细胞LH超过3小时，而在GnRH预处理的细胞中为27.4 +/-1.2%）;但是，在此情况下，响应释放激素的磷酸肌醇（IP）的产生保持不受影响（1 μ M GnRH在对照细胞中引起45分钟后IP积累高于基础水平161 +/- 9%，在GnRH预处理的细胞中为162 +/- 11%）。用NaF预处理垂体细胞培养物（鸟苷酸结合蛋白激活剂，10 mM，3 h）也降低了随后GnRH刺激的LH释放，此外，还引起GnRH受体数量减少，GnRH受体亲和力增加，GnRH刺激的IP产生减少至基础水平，以及响应于钙离子载体A23187的刺激而释放的LH量的增加。为了确定LH释放的变化是否是IP产生减少和/或GnRH受体结合减少的结果，评估了这些过程恢复至对照水平的时间过程。氟化钠预处理后，GnRH受体结合率继续下降，在预处理后6 h达到最低点（对照的62%），并在48 h恢复（对照的90%）。相反，GnRH引起的IP积累没有恢复到对照水平，即使在NaF预处理后恢复48小时后（1 μ M GnRH刺激的IP积累在NaF预处理的细胞中是57%，与对照细胞相比，恢复48小时后）。GnRH刺激的LH释放在NaF预处理后立即被抑制（NaF预处理的细胞中1 μ M GnRH刺激的LH释放是对照水平的65%）。细胞在3小时内开始恢复（对照的80%），到6小时几乎完全恢复（对照的90%）。A23187刺激的LH释放在NaF预处理后立即增强（NaF预处理的细胞中30 μ M A23187刺激的LH释放是对照水平的170%）。对离子载体的反应是133%的控制0.5小时，并在1小时内测量完全恢复（100%的控制）。此外，NaF和GnRH预处理仍然引起促性腺激素反应性下降时，IP生产被磷脂酶C抑制剂U-73122抑制。结果表明，促性腺激素脱敏（通过氟化钠或GnRH预处理）的发展可以从IP生产的变化中解耦。此外，由于从氟化钠引起的GnRH脱敏、A23187致敏和GnRH受体结合减少中恢复的时间过程不同，这些过程似乎是通过不同的机制发生的，这表明在促性腺细胞中可能存在鸟苷酸结合蛋白作用的多个位点。
After initial GnRH pretreatment (10 nm, 5 h), subsequent GnRH-stimulated LH release from the gonadotrope was diminished (1 muM GnRH stimulated release of 36.4 +/- 1.4% total cellular LH over 3 h in cells initially pretreated with.medium alone compared to 27.4 +/- 1.2% in GnRH-pretreated cells); however, inositol phosphate (IP) production in response to the releasing hormone remained unaffected (1 muM GnRH provoked IP accumulation of 161 +/- 9% above basal levels after 45 min in control cells and 162 +/- 11% in GnRH-pretreated cells). Pretreatment of pituitary cell cultures with NaF (a guanyl nucleotide binding protein activator, 10 mM, 3 h) also decreased subsequent GnRH-stimulated LH release, and in addition, provoked a decrease in GnRH receptor number, an increase in GnRH receptor affinity, reduction of GnRH-stimulated IP production to basal levels, and an increase in the amount of LH released in response to stimulation with the calcium ionophore A23187. In order to determine if the changes in LH release were a result of decreased IP production and/or decreased GnRH receptor binding, the time course of recovery to control levels of these processes was assessed. GnRH receptor binding continued to decrease after NaF pretreatment, reaching a nadir (62% of control) at 6 h after the pretreatment period and recovering at 48 h (90% of control). In contrast, GnRH-provoked IP accumulation did not return to control levels even after 48 h of recovery after NaF pretreatment (1 muM GnRH-stimulated IP accumulation in NaF-pretreated cells was 57% compared to control cells after 48 h of recovery). GnRH-stimulated LH release was inhibited immediately after NaF pretreatment (1 muM GnRH-stimulated LH release in NaF-pretreated cells was 65% of control levels). Cells began to recover within 3 h (80% of control) and were almost completely recovered by 6 h (90% of control). A23187-provoked LH release was enhanced immediately after NaF pretreatment (30 muM A23187-stimulated LH release in NaF-pretreated cells was 170% of control levels). Responsiveness to ionophore was 133% of control by 0.5 h, and complete recovery was measured within 1 h (100% of control). Furthermore, both NaF and GnRH pretreatment still provoked a decrease in gonadotrope responsiveness when IP production was inhibited by the phospholipase C inhibitor U-73122. The results suggest that the development of gonadotrope desensitization (by either NaF or GnRH pretreatment) can be uncoupled from changes; in IP production. In addition, because the time courses of recovery from NaF-provoked desensitization to GnRH, sensitization to A23187, and decreased GnRH receptor binding are different, it appears that these processes occur by different mechanisms, suggesting that there may be multiple sites of guanyl nucleotide binding protein action in the gonadotrope.