title: Coupling of adrenal medullary opioid receptors to islet-activating protein-sensitive GTP-binding proteins.
abstract: Possible coupling of bovine adrenal medullary opioid receptors to islet-activating protein (IAP, pertussis toxin)-sensitive GTP-binding proteins was investigated by studying effects of guanyl-5'-yl imidodiphosphate (Gpp(NH)p) and IAP treatment of membranes on opioid binding. Gpp(NH)p inhibited [3H]D-Ala2-D-Leu5-enkephalin ([3H]DADLE) binding by increasing the dissociation constant of [3H]DADLE and membranes, and enhanced slightly [3H]diprenorphine binding. IAP treatment of membranes reduced [3H]DADLE binding and abolished almost completely the Gpp(NH)p inhibition of [3H]DADLE binding. Treatment of membranes with IAP and [32P]NAD resulted in radio-labeling of membrane proteins of approximately 39,000 dalton. DADLE inhibited adenylate cyclase activity in rat brain caudate nucleus. However, DADLE, beta-endorphin, levorphanol and dynorphin A(1-13) did not show any significant inhibitory action on bovine adrenal medullary adenylate cyclase activity. These results suggest that bovine adrenal medullary opioid (DADLE) receptors are linked to IAP-sensitive GTP-binding proteins which are not directly coupled to adenylate cyclase.
mesh_terms: D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D000313:Adrenal Medulla / Q000032:analysis*; D000818:Animals; D002417:Cattle; D004174:Diprenorphine / Q000378:metabolism; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine; D019204:GTP-Binding Proteins / Q000032:analysis*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D037342:Pertussis Toxin; D011957:Receptors, Opioid / Q000032:analysis*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D011957:Receptors, Opioid; D010566:Virulence Factors, Bordetella; D004174:Diprenorphine; D006165:Guanylyl Imidodiphosphate; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins