Jinnah H A, Conn P M
Endocrinology. 1986 Jun;118(6):2599-604. doi: 10.1210/endo-118-6-2599.
GnRH stimulates LH release from pituitary gonadotropes. Prolonged exposure of these cells to GnRH results in decreased sensitivity to further stimulation by the releasing hormone both in vivo and in vitro. Chelation of extracellular Ca++ with EGTA blocks GnRH-stimulated LH release but does not prevent subsequent desensitization. Desensitization occurs when cells are preincubated in EGTA containing 10(-7) M GnRH for a variety of times (20 min to 12 h) or when cells are preincubated for 3 h in EGTA with 10(-10), 10(-9), or 10(-8) M GnRH. A GnRH antagonist does not cause desensitization to GnRH and blocks desensitization in response to GnRH in the Ca++-free medium. Preincubation in EGTA containing 10(-7) M GnRH for 3 h did not alter sensitivity of cells to sn 1,2 dioctanoylglycerol (a protein kinase C activator), Ca++ ionophore A23187, or veratridine (an activator of endogenous ion channels). These results suggest that desensitization results from occupancy of the GnRH receptor by an agonist and may be uncoupled from LH release.
促性腺激素释放激素（GnRH）刺激垂体促性腺细胞释放促黄体生成素（LH）。这些细胞长时间暴露于GnRH会导致其在体内和体外对释放激素的进一步刺激敏感性降低。用乙二醇双四乙酸（EGTA）螯合细胞外钙离子可阻断GnRH刺激的LH释放，但不能阻止随后的脱敏作用。当细胞在含有10^(-7)M GnRH的EGTA中预孵育不同时间（20分钟至12小时），或在含有10^(-10)、10^(-9)或10^(-8)M GnRH的EGTA中预孵育3小时时，脱敏作用就会发生。GnRH拮抗剂不会导致对GnRH的脱敏，并且在无钙离子培养基中可阻断对GnRH的脱敏反应。在含有10^(-7)M GnRH的EGTA中预孵育3小时不会改变细胞对1,2 - 二辛酰甘油（一种蛋白激酶C激活剂）、钙离子载体A23187或藜芦碱（一种内源性离子通道激活剂）的敏感性。这些结果表明，脱敏作用是由激动剂占据GnRH受体引起的，并且可能与LH释放解偶联。
