title: Opioid activities of fragments of beta-endorphin and of its leucine65-analogue. Comparison of the binding properties of methionine- and leucine-enkephalin.
abstract: For characterisation in vitro, four parallel assays were used: the guinea-pig ileum and mouse vas deferens as pharmacological models at 36 degrees C and the inhibition of binding of [3H]-naltrexone, [3H]-leucine-enkephalin and [3H]-methione-enkephalin at 0 degrees C. The Leu65-analogue of beta-andorphin and its fragments (61-65, 61-76 and 61-77) have a lower affinity to the [3H]-naltrexone binding site of mu-receptors than the corresponding Met65-peptides wereheas no such difference was found for the [3H]leucine-enkephalin binding sites or delta-receptors. When the binding of [3H]-methionine-enkephalin or [3H]-leucine-enkephalin was inhibited by cold ligands interacting with delta-, mu-, or kappa-receptors, no evidence was obtained for more than one type of delta-binding site.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects; D004723:Endorphins / Q000378:metabolism* / Q000494:pharmacology*; D004745:Enkephalins / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007930:Leucine / Q000378:metabolism; D008024:Ligands; D008715:Methionine / Q000378:metabolism; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D013552:Swine; D008083:beta-Lipotropin / Q000494:pharmacology
chemical_list: D004723:Endorphins; D004745:Enkephalins; D008024:Ligands; D008083:beta-Lipotropin; D008715:Methionine; D007930:Leucine