Opioid activities of human beta-casomorphins.
Opioid activities of human beta-casomorphin-4, -5, -7 and -8 and, for comparison, of the corresponding bovine beta-casomorphins were studied in the guinea-pig ileum preparation. Binding parameters, i.e. KD-values and binding site concentrations, for the interaction of human and bovine beta-casomorphins with opioid receptors in rat brain homogenates were determined in inhibition experiments, using [3H]-(D-Ala2, MePhe4, Gly-ol5)enkephalin, [3H]-(D-Ala2, D-Leu5)enkephalin and [3H]ethylketazocin as mu-, delta- and kappa-opioid receptor ligands. Analysis of binding data was performed using a non-linear curve fitting program. All beta-casomorphins examined displayed opioid activity. The affinity was highest for mu-receptors, less so for delta-receptors and lowest for kappa-receptors. It is suggested that human beta-casomorphins might play a role as "food hormones".
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D004723:Endorphins / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D007082:Ileum / Q000187:drug effects*; D066298:In Vitro Techniques; D009130:Muscle, Smooth / Q000378:metabolism; D009197:Myenteric Plexus / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects* / Q000378:metabolism; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu
D004723:Endorphins; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu