Multiple molecular forms of stereospecific opiate binding
Smith, A.P.; Loh, H.H.
Molecular Pharmacology 16(3): 757-766
1979
ISSN/ISBN: 0026-895X PMID: 43467 Document Number: 147893
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 MW and several other species of less than 20,000 MW. Iso-electric focusing resolved the binding components into 2 major peaks of pI about 8.4 and 3.2, and several minor species in the pI range 8.3-6.5; both high and low MW material appeared to be present in the 2 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+. Comparable heterogeneity was observed in material stereospecifically binding 3H-.beta./H-endorphin, 3H-etorphine and 3H-naloxone, and incubation of Brij-extracted 3H-.beta.H-endorphin-binding membranes with 10 mM dimethyl suberimidate covalently labeled a broad range of species of 2-200 .times. 103 MW. Many distinct brain membrane components can bind opiates stereospecifically in vitro; these components may include lipids and proteins.