When brain membranes were incubated in vitro with 3H-enkephalinamide, then extracted with the non-ionic detergent Brij 36-T, up to 75% of the levorphanol-displaceable radioactivity was released in a bound form. Analysis of the binding material by gel filtration revealed a broad peak of 100,000-500,000 molecular weight, and several other species of less than 20,000 molecular weight. Iso-electric focusing resolved the binding components into two major peaks of pI's about 8.4 and 3.2, and several minor species in the pI range 8.3-6.5; both high and low molecular weight material appeared to be present in the two major pI peaks. All of the stereospecific binding components identified by isoelectric focusing appeared to behave similarly with respect to several competing unlabeled drugs, and to Na+ ion. Comparable heterogeneity was observed in material stereospecifically binding 3H-βH-endorphin, 3H-etorphine, and 3H-naloxone, and incubation of Brij-extracted 3H-βH-endorphine-binding membranes with 10 mM dimethyl suberimidate covalently labeled a broad range of species of 2-200 x 103 molecular weight. These results demonstrate that many distinct brain membrane components can bind opiates stereospecifically in vitro; these components may include lipids as well as proteins.
|Original language||English (US)|
|Number of pages||10|
|State||Published - Dec 1 1979|