Konno F, Takayanagi I
Arch Int Pharmacodyn Ther. 1987 May;287(1):5-15.
Interactions of several alpha 1-adrenoceptor agonists and antagonists were studied in rabbit iris dilator smooth muscles and aortic strips using radioligand binding techniques. The specific binding of [3H]-prazosin to the membrane preparations of both tissues is of high affinity, saturable with a single binding site, has characteristics expected of alpha 1-adrenoceptors. pKi-Values of prazosin and yohimbine and the pKD-value of [3H]-prazosin in the rabbit dilators, however, were significantly lower than those in the aortic strips, while pKi-values of phentolamine, clonidine and norepinephrine in the dilators were nearly equal to those in the aortic strips. Although the efficacy of norepinephrine in the dilators was significantly less than that in the aortic strips, the maximum binding sites for [3H]-prazosin to the membrane preparations from the rabbit dilators were more numerous than those from the aortic strips. Therefore, it is likely that the intrinsic efficacy of norepinephrine in the dilators is less than that in the aortic strips. These results suggest that alpha 1-adrenoceptors in the rabbit dilator smooth muscle and the aortic strips may not be identical and that both selective and nonselective drugs, which act on these receptor sites, may exist.
采用放射性配体结合技术，研究了几种α1-肾上腺素能受体激动剂和拮抗剂在兔虹膜开大肌平滑肌和主动脉条中的相互作用。[3H]-哌唑嗪与两种组织膜制剂的特异性结合具有高亲和力，可被单一结合位点饱和，具有α1-肾上腺素能受体预期的特征。然而，哌唑嗪和育亨宾的pKi值以及[3H]-哌唑嗪在兔虹膜开大肌中的pKD值明显低于主动脉条中的值，而酚妥拉明、可乐定和去甲肾上腺素在虹膜开大肌中的pKi值与主动脉条中的值几乎相等。尽管去甲肾上腺素在虹膜开大肌中的效能明显低于主动脉条中的效能，但[3H]-哌唑嗪与兔虹膜开大肌膜制剂的最大结合位点比主动脉条中的更多。因此，去甲肾上腺素在虹膜开大肌中的内在效能可能低于主动脉条中的。这些结果表明，兔虹膜开大肌平滑肌和主动脉条中的α1-肾上腺素能受体可能不相同，并且可能存在作用于这些受体位点的选择性和非选择性药物。
