Siegel H, Triggle D J
Life Sci. 1982 May 10;30(19):1645-52. doi: 10.1016/0024-3205(82)90497-0.
A comparison was made of muscarinic receptor occupancy by the irreversible antagonist benzilylcholine mustard (BCM) as determined from shifts in the dose-response curve to a muscarinic agonist and from 3H-QNB binding to homogenates of BCM-treated tissue. Major discrepancies were found. A low concentration of BCM (3x10-8M/15 min.) produced a parallel dose-response curve shift corresponding to 98-99% receptor occupancy by BCM, whereas 3H-QNB binding revealed only 48% receptor occupancy. Possible origins of this discrepancy are discussed. High concentrations of BCM (5x10-5M, 15 min.) fail to completely alkylate all 3H-QNB binding sites even though response is completely lost. Although significant (64%) recovery of response occurs after prolonged tissue washing (240 min.) this is not accompanied by an increase in 3H-QNB binding. The small fraction (approximately 5%) of sites inaccessible to BCM and with reduced affinity for 3H-QNB may represent a subpopulation of muscarinic receptors.
通过剂量-反应曲线向毒蕈碱激动剂的位移以及3H-QNB与经BCM处理的组织匀浆的结合来确定不可逆拮抗剂苯甲酰胆碱氮芥（BCM）对毒蕈碱受体的占有率，并进行了比较。发现了主要差异。低浓度的BCM（3×10-8M/15分钟）产生了平行的剂量-反应曲线位移，对应于BCM对98-99%的受体占有率，而3H-QNB结合仅显示48%的受体占有率。讨论了这种差异的可能来源。高浓度的BCM（5×10-5M，15分钟）即使反应完全丧失也不能完全烷基化所有3H-QNB结合位点。尽管经过长时间的组织洗涤（240分钟）后反应有显著（64%）的恢复，但这并未伴随着3H-QNB结合的增加。BCM无法作用且对3H-QNB亲和力降低的一小部分位点（约5%）可能代表了毒蕈碱受体的一个亚群。
