豚鼠胃平滑肌毒蕈碱受体的多样性

从豚鼠胃平滑肌收缩实验测得,胃底、体部纵、环肌的乙酰胆碱pD₂约为6.5和4.0,阿托品的pA₂约为10和8.5。实验结果提示胃平滑肌上存在高、低两种不同亲和力的毒蕈碱受体,分别与胃底、体部的纵、环肌收缩有关。又用Yamamura法对豚鼠胃平滑肌组织中的毒蕈碱受体进行了检定,测得解离常数KD值约为1.8和18 nm的两种组分。由于作用不同的蛋白质修饰剂,对这两种组分与标记配体结合的影响不同,故认为它们是亲和力不同的两种特异结合部位。

POLYMORPHISM OF THE AFFINITY OF MUSCARINIC RECEPTORS IN THE GASTRIC SMOOTH MUSCLES OF GUINEA PIGS

In the experiment of contraction of guinea pig gestric smooth muscle, it was found that pD_2 of acetylcholine for longitudinal and circular smooth muscles from guinea pig gastric fundus and body were 6.5 and 4.0 respectively. ThepA_2 values of atropine for these smooth muscles were approximately 10 and 8.5 respectively. This suggests that there were two kinds of muscarinic receptars of different affinities in the stomach and these receptors played a role in contractile function in longitudinal and circular smooth muscles. Specific [~3H]-QNB binding tohomogenates of gastric smooth muscles were also studied by using the method described by Yamamura et al. It was also found that high and low affinity bindings in the homogenates of gastric smooth muscles. The KD values of various homogenates of high and low affinity bindings were 1.8 and 18 nmc/L respectively. Since protein modulators with various functions showed different effects of the bindings of two components to labeled ligand, it is therefore concluded that the two components were the binding sites with different affinities.