Suslova I V, Iarygin K N
Zh Evol Biokhim Fiziol. 1994 Jan-Feb;30(1):53-61.
Radioligand analysis of ventricular membranes from the frog Rana temporaria with muscarinic antagonist 3H-QNB (qunuclidinul benzilate) revealed homogeneous population of highly specific muscarinic receptors with high affinity (Kd = 0.502 +/- 0.020 nM and Bmax = 789 +/- 18 fmol/mg protein). Competitive binding of M1-antagonist pirenzepine revealed two binding sites on the membrane with Kd values 5.6 +/- 1.7 and 237 +/- 45 nM, and total capacity of 20.6 +/- 10.2 and 742 +/- 58 fmol/mg protein respectively, which may be attributed to M1- and M2-subtypes in accordance with Receptor Nomenclature. The inhibitory effect of pirenzepine on negative inotropic action of Ach has been studied in the intact electrically stimulated ventricle. Analysis of the data by Schild procedure showed that KB for pirenzepine is equal to 13.9 +/- 2.4 nM. The results obtained suggest that the frog ventricle contains muscarinic cholinoreceptors of M2-subtype (possibly, M4-subtype) which account for negative inotropic effect of Ach. Small population of M1-like receptors was also revealed, their functional role still remaining obscure.
用毒蕈碱拮抗剂3H-QNB（喹核醇苯甲酸盐）对林蛙心室膜进行放射性配体分析，结果显示存在均一的高亲和力毒蕈碱受体群体（Kd = 0.502 +/- 0.020 nM，Bmax = 789 +/- 18 fmol/mg蛋白）。M1拮抗剂哌仑西平的竞争性结合显示膜上有两个结合位点，Kd值分别为5.6 +/- 1.7和237 +/- 45 nM，总容量分别为20.6 +/- 10.2和742 +/- 58 fmol/mg蛋白，根据受体命名法，这可能分别归因于M1和M2亚型。在完整的电刺激心室中研究了哌仑西平对乙酰胆碱负性肌力作用的抑制作用。用Schild法分析数据表明，哌仑西平的KB等于13.9 +/- 2.4 nM。所得结果表明，蛙心室含有M2亚型（可能是M4亚型）的毒蕈碱胆碱能受体，其介导了乙酰胆碱的负性肌力作用。还发现了少量M1样受体，其功能作用仍不清楚。
