Baumann R, Kuhl H
Acta Endocrinol (Copenh). 1979 Oct;92(2):228-41. doi: 10.1530/acta.0.0920228.
The specific binding of [125I]LH-RH to isolated plasma membranes of rat pituitaries was investigated. The binding process was found to be highly specific, temperature-dependent and saturable. The dissociation constant as caluclated by three different methods was approximately 1.3 . 10(-8) M, indicating a single type of binding sites. Maximal binding capacity was 1 . 10(-12 moles/mg protein (= 2 ng LH-RH/pituitary gland), and the number of binding sites was calculated to be 6 . 10(11) per mg membrane protein (=1 . 10(10) binding sites/pituitary gland). When diluted with ice-cold buffer the dissociation of specifically bound LH-RH occurred very rapidly (half-life 3.17 min) with a rate constant of 0.219 min-1. The dissociation process followed first-order kinetics. Specificity of binding was demonstrated by dose-dependent competition of unlabelled LH-RH, the highly potent analogue D-glutamine-(cyclohexyl)6-LH-RH-nonapeptide-ethylamide and the fragment of an analogue (6-D-Ser(TBu))-LH-RH-(3-9)-heptapeptide-ethylamide with the binding [125I]LH-RH, while angiotensin I, II, oxytocin and bacitracin did not compete. The affinities of LH-RH and the analogue to the binding sites of the pituitary plasma membranes were not consistent with the respective biological activities.
研究了[125I]促黄体激素释放激素（LH-RH）与大鼠垂体分离的质膜的特异性结合。发现结合过程具有高度特异性、温度依赖性且可饱和。通过三种不同方法计算的解离常数约为1.3×10^(-8) M，表明存在单一类型的结合位点。最大结合容量为1×10^(-12)摩尔/毫克蛋白质（= 2纳克LH-RH/垂体），结合位点数量经计算为每毫克膜蛋白6×10^11个（= 1×10^10个结合位点/垂体）。当用冰冷缓冲液稀释时，特异性结合的LH-RH的解离非常迅速（半衰期3.17分钟），速率常数为0.219分钟^(-1)。解离过程遵循一级动力学。未标记的LH-RH、高效类似物D-谷氨酰胺-（环己基）6-LH-RH-九肽乙酰胺以及类似物片段（6-D-丝氨酸（叔丁基））-LH-RH-（3-9）-七肽乙酰胺与结合的[125I]LH-RH存在剂量依赖性竞争，证明了结合的特异性，而血管紧张素I、II、催产素和杆菌肽则无竞争作用。LH-RH及其类似物对垂体质膜结合位点的亲和力与各自的生物学活性不一致。
