Pfeiffer A, Sadée W, Herz A
J Neurosci. 1982 Jul;2(7):912-7. doi: 10.1523/JNEUROSCI.02-07-00912.1982.
The effects of Na+, guanyl-5'-yl imidodiphosphate (Gpp(MH)p), and Mn2+ on the binding of dihydromorphine, ethylketocyclazocine, D-Ala2, D-Leu5-enkephalin, and diprenorphine to the opiate receptor were investigated. Three distinct binding sites, mu, delta, and kappa sites, were identified with the use of multiple tracer displacement curves. Moreover, this approach was used to determine the effects of Gpp (NH)p and metal ions on each individual binding site. At the mu and delta sites, Na+ and Gpp(NH)p each decreased and Mn2+ increased agonist binding affinities, with the exception of D-Ala2, D-Leu-enkephalin affinity which was not affected by Gpp(NH)p. None of these conditions markedly altered dihydromorphine and D-Ala2, Leu5-enkephalin binding to kappa sites, whereas the affinity of ethylke-tocyclazocine for kappa sites was decreased by Gpp(NH)p. Sodium ions lowered the capacity of mu sites and Gpp(NH)p reduced that of delta sites, while both agents increased the capacity of apparent kappa sites. These results demonstrate that each of the kinetically distinguishable binding sites is regulated differentially by metal ions and guanyl nucleotides. Simultaneous addition of Na+ and Gpp(NH)p greatly reduced the binding affinity of all three agonists at their respective high affinity sites (dihydromorphine at the mu site, D-Ala2, D-Leu5-enkephalin at the delta site, and ethylketocyclazocine at the kappa and mu sites). This result confirms previous observations that agonist binding is characterized by a large affinity reduction in the presence of both Na+ and guanyl nucleotides, and it extends this concept to each of the opiate receptor subtypes.
研究了Na⁺、鸟苷-5'-基亚氨基二磷酸（Gpp(MH)p）和Mn²⁺对二氢吗啡、乙基酮环唑辛、D-丙氨酸²、D-亮氨酸⁵-脑啡肽和二丙诺啡与阿片受体结合的影响。使用多种示踪剂置换曲线确定了三个不同的结合位点，即μ、δ和κ位点。此外，该方法用于确定Gpp(NH)p和金属离子对每个单独结合位点的影响。在μ和δ位点，Na⁺和Gpp(NH)p均降低激动剂结合亲和力，而Mn²⁺增加激动剂结合亲和力，但D-丙氨酸²、D-亮氨酸-脑啡肽亲和力不受Gpp(NH)p影响。这些条件均未显著改变二氢吗啡和D-丙氨酸²、亮氨酸⁵-脑啡肽与κ位点的结合，而Gpp(NH)p降低了乙基酮环唑辛与κ位点的亲和力。钠离子降低了μ位点的容量，Gpp(NH)p降低了δ位点的容量，而两种试剂均增加了表观κ位点的容量。这些结果表明，每个动力学上可区分的结合位点受金属离子和鸟苷核苷酸的调节方式不同。同时添加Na⁺和Gpp(NH)p极大地降低了所有三种激动剂在其各自高亲和力位点（二氢吗啡在μ位点、D-丙氨酸²、D-亮氨酸⁵-脑啡肽在δ位点、乙基酮环唑辛在κ和μ位点）的结合亲和力。该结果证实了先前的观察结果，即激动剂结合的特征是在同时存在Na⁺和鸟苷核苷酸时亲和力大幅降低，并将这一概念扩展到每种阿片受体亚型。
