Gut S H, Demoliou-Mason C D, Hunter J C, Hughes J, Barnard E A
MRC Molecular Neurobiology Unit, MRC Center, Cambridge, U.K.
Eur J Pharmacol. 1989 Oct 17;172(4-5):339-46. doi: 10.1016/0922-4106(89)90014-x.
Cholecystokinin (CCK) binding sites were solubilized from pig cerebral cortical membranes with digitonin (2%, w/v) in the presence of Na+ (120 mM) and Mg2+ (5 mM). Scatchard plot transformation of equilibrium binding data obtained with 125I-CCK-8S gave an apparent dissociation constant (Kd) of 0.6 nM, comparable to that obtained in membranes in the presence of these cations. Hill coefficients close to unity suggested the presence of a single population of receptor sites. Competitive inhibition studies with pentagastrin, gastrin(1-17)S and the CCKA receptor antagonist L-364,718 indicated that the solubilized receptor sites were of the B-type (CCKB), with the same pharmacological profile as that observed in membranes. Optimal specific binding of 125I-CCK-8S to membrane-bound and solubilized receptors was obtained in the presence of divalent cations. Both the membrane-bound and the solubilized receptor activity were attenuated by guanylyl-imidodiphosphate (Gpp(NH)p) indicating that the brain CCKB receptors are coupled to G proteins.
用洋地黄皂苷（2%，w/v）在Na⁺（120 mM）和Mg²⁺（5 mM）存在的条件下从猪大脑皮层膜中溶解胆囊收缩素（CCK）结合位点。用¹²⁵I-CCK-8S获得的平衡结合数据的Scatchard图转换得出表观解离常数（Kd）为0.6 nM，与在这些阳离子存在下在膜中获得的结果相当。接近1的希尔系数表明存在单一的受体位点群体。用五肽胃泌素、胃泌素（1-17）S和CCKA受体拮抗剂L-364,718进行的竞争性抑制研究表明，溶解的受体位点是B型（CCKB），其药理学特征与在膜中观察到的相同。在二价阳离子存在的情况下获得了¹²⁵I-CCK-8S与膜结合和溶解受体的最佳特异性结合。鸟苷酰亚胺二磷酸（Gpp(NH)p）减弱了膜结合和溶解的受体活性，表明脑CCKB受体与G蛋白偶联。
