Smith J R, Simon E J
Proc Natl Acad Sci U S A. 1980 Jan;77(1):281-4. doi: 10.1073/pnas.77.1.281.
Stereospecific binding of 3H-labeled [D-Ala2,D-Leu5]enkephalin is irreversibly inactivated by the sulfhydryl group alkylating agent N-ethylmaleimide. This inactivation, like that of opiate binding, exhibits pseudo-first-order kinetics with a half-inactivation time of 10-12 min. The presence of opiates or enkephalins during incubation with N-ethylmaleimide provides good protection. Ouantitative studies of protection demonstrate that naltrexone and morphine are 20 and 8 times, respectively, more effective in protecting the binding of [3H]naltrexone than that of [3H]enkephalin. [D-Ala2,Leu]Enkephalin and [D-Ala2,Met]enkephalin, however, are more effective (7 and 30 times, respectively) for the protection of 3H-labeled [D-Ala2,D-Leu5]enkephalin binding. These results provide strong evidence for the existence of two classes of opiate receptor in rat brain.
3H标记的[D-丙氨酸2,D-亮氨酸5]脑啡肽的立体特异性结合可被巯基烷基化剂N-乙基马来酰亚胺不可逆地灭活。这种灭活作用,与阿片类结合的灭活作用一样,呈现伪一级动力学,半灭活时间为10 - 12分钟。在与N-乙基马来酰亚胺孵育期间存在阿片类或脑啡肽可提供良好的保护作用。保护作用的定量研究表明,纳曲酮和吗啡在保护[3H]纳曲酮结合方面分别比保护[3H]脑啡肽结合有效20倍和8倍。然而,[D-丙氨酸2,亮氨酸]脑啡肽和[D-丙氨酸2,甲硫氨酸]脑啡肽在保护3H标记的[D-丙氨酸2,D-亮氨酸5]脑啡肽结合方面更有效(分别为7倍和30倍)。这些结果为大鼠脑中存在两类阿片受体提供了有力证据。