title: Beta-endorphin: opiate receptor binding activities of six naturally occurring beta-endorphin homologs studied by using tritiated human hormone and naloxone as primary ligands--effects of sodium ion.
abstract: Six naturally occurring homologs of beta-endorphin were tested for their potency in inhibiting the binding of [3H]naloxone and [3H]-beta h-endorphin either in the presence or in the absence of Na+. Sodium ion reduces inhibitory potency of these homologs against [3H]-beta h-endorphin and [3H]naloxone to about the same extent. The ratio of the IC50 obtained with Na+ to that obtained without Na+ is not highly correlated with analgesic potency. Very high (greater than 300) sodium ratios are observed with some homologs. A significant rank correlation was found between the ratio of the relative potency in displacing [3H]beta h-endorphin to the relative potency in analgesia and potency in inhibiting the binding of the pure antagonist naloxone.
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001717:Birds / Q000378:metabolism; D002162:Camelus / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000378:metabolism*; D006736:Horses / Q000378:metabolism; D006801:Humans; D009270:Naloxone / Q000378:metabolism*; D011957:Receptors, Opioid / Q000378:metabolism*; D012474:Salmon / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology*; D013045:Species Specificity; D014422:Turkeys / Q000378:metabolism
chemical_list: D004723:Endorphins; D011957:Receptors, Opioid; D009270:Naloxone; D012964:Sodium