Clayton R N, Shakespear R A, Marshall J C
Mol Cell Endocrinol. 1978 Jun;11(1):63-78. doi: 10.1016/0303-7207(78)90033-3.
Purified bovine pituitary plasma membranes possess two specific LH-RH binding sites. The high affinity site (2.5 X 10(9) l/mol) has low capacity (9 X 10(-15) mol/mg membrane protein) while the low affinity site 6.1 X 10(5) l/mol) has a much higher capacity (1.1 X 10(-10) mol/mg). Specific LH-RH binding to plasma membranes is increased 8.5-fold during purification from homogenate whilst adenylate cyclase activity is enriched 7--8-fold. Distribution of specific LH-RH binding to sucrose density gradient interface fractions parallels that of adenylate cyclase activity. Mg2+ and Ca2+ inhibit specific [125I]LH-RH binding at micromolar concentrations. Synthetic LH-RH, up to 250 microgram/ml, failed to stimulate adenylase cyclase activity of the purified bovine membranes. Using a crude 10,800 g rat pituitary membrane preparation, LH-RH similarly failed to activate adenylate cyclase even in the presence of guanyl nucleotides. These data confirm the presence of LH-RH receptor sites on pituitary plasma membranes and suggest that LH-RH-induced gonadotrophin release may be mediated by mechanisms other than activation of adenylate cyclase.
纯化的牛垂体质膜具有两个特异性促黄体生成素释放激素（LH-RH）结合位点。高亲和力位点（2.5×10⁹升/摩尔）容量较低（9×10⁻¹⁵摩尔/毫克膜蛋白），而低亲和力位点（6.1×10⁵升/摩尔）容量则高得多（1.1×10⁻¹⁰摩尔/毫克）。从匀浆中纯化过程中，质膜上特异性LH-RH结合增加了8.5倍，同时腺苷酸环化酶活性富集了7至8倍。特异性LH-RH与蔗糖密度梯度界面组分的结合分布与腺苷酸环化酶活性的分布平行。镁离子和钙离子在微摩尔浓度下抑制特异性[¹²⁵I]LH-RH结合。高达250微克/毫升的合成LH-RH未能刺激纯化牛膜的腺苷酸环化酶活性。使用粗制的10,800克大鼠垂体膜制剂，即使存在鸟苷酸，LH-RH同样未能激活腺苷酸环化酶。这些数据证实了垂体质膜上存在LH-RH受体位点，并表明LH-RH诱导的促性腺激素释放可能由腺苷酸环化酶激活以外的机制介导。
