title: beta-Endorphin: characterization of binding sites specific for the human hormone in human glioblastoma SF126 cells.
abstract: The established human glioblastoma cell line SF126 was found to bind tritiated human beta-endorphin (beta h-EP) in a saturable fashion. From displacement studies, the ED50 was estimated to be about 2.5 nM. The Kd was estimated as 1.9 X 10(-9) M and Scatchard analysis showed a biphasic pattern with a predominant low-affinity component. Binding reached a maximum at about 90 min at 22 degrees C and was instantaneously reversible. Tritiated [D-Ala2,D-Leu5]enkephalin and tritiated dihydromorphine did not bind to the cells. Sodium at a concentration of 150 mM decreased the specific binding by 80%. The interaction with the cellular binding site appeared to be mediated by the COOH-terminal segment of beta h-EP, as beta h-EP-(6-31) retained a high potency for displacing tritiated beta h-EP, and beta h-EP-(1-27) has no activity. Camel beta-EP was only about 1% as active as the human hormone.
mesh_terms: D001667:Binding, Competitive; D002478:Cells, Cultured; D004723:Endorphins / Q000378:metabolism*; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D011957:Receptors, Opioid / Q000378:metabolism*; D013329:Structure-Activity Relationship; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D011957:Receptors, Opioid; D001615:beta-Endorphin