title: A new photoaffinity probe, 4-amino-2-[4-(4-azidocinnamoyl)piperazino]-6,7-dimethoxyqu inazoline, for alpha 1-adrenoceptors.
abstract: A photoaffinity probe for alpha 1-adrenoceptors was synthesized and its properties examined on rat brain membrane preparations. The binding of 4-amino-2-[4-(4-azidocinnamoyl)piperazino]-6,7-dimethoxyquin azoline (ACP) to these receptors was of high affinity (KD = 1.05 nM) and reversible in the dark. A dose-dependent decrease in the concentration of [3H]prazosin binding sites without a change in KD was observed when membranes were preincubated with ACP, photolyzed, and then extensively washed prior to assay. This reduction in receptor concentration was prevented by alpha 1-adrenergic ligands. The specificity of ACP for alpha 1-receptors was further demonstrated by its inability to compete with [3H]dihydroalprenolol and [3H]yohimbine binding in these same membranes. Also, the concentrations and affinity constants of beta-adrenoceptors and alpha 2-adrenoceptors were unaffected in membranes which had been photolyzed after preincubation with ACP. No reduction in concentration of alpha 1-adrenoceptors was detected if ACP was photolyzed prior to incubation with receptors or if ACP was maintained in darkness throughout the experiment. The results suggest that ACP is a specific and sensitive photoprobe that may be useful for further studies on alpha 1-adrenoceptor coupled systems and that may be particularly suited for use in cell culture work.
mesh_terms: D000345:Affinity Labels / Q000138:chemical synthesis; D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D055598:Chemical Phenomena; D002621:Chemistry; D004082:Dihydroalprenolol / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008566:Membranes / Q000187:drug effects; D011224:Prazosin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013056:Spectrophotometry, Ultraviolet; D015016:Yohimbine / Q000378:metabolism
chemical_list: D000345:Affinity Labels; D011942:Receptors, Adrenergic, alpha; C049247:4-amino-2-(4-(4-azidocinnamoyl)piperazino)-6,7-dimethoxyquinazoline; D015016:Yohimbine; D004082:Dihydroalprenolol; D011224:Prazosin