Selective protection of stereospecific enkephalin and opiate binding against inactivation by N-ethylmaleimide: evidence for two classes of opiate receptors.

摘要: Abstract 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 opiate binding, exhibits pseudo-first-order kinetics with a half-inactivation time 10-12 min. The presence opiates or enkephalins during incubation N-ethylmaleimide provides good protection. Ouantitative studies protection demonstrate naltrexone and morphine are 20 8 times, respectively, more effective in protecting [3H]naltrexone than [3H]enkephalin. [D-Ala2,Leu]Enkephalin [D-Ala2,Met]enkephalin, however, (7 30 respectively) for binding. These results provide strong evidence existence two classes receptor rat brain.