title: p-Azidoclonidine: a photoaffinity label for the alpha 2-adrenoceptor.
abstract: We have synthesized and characterized p-azidoclonidine (AZC) as a putative alpha 2-adrenoceptor photoaffinity label. [3H]AZC demonstrated high affinity (KD = 11.8 +/- 2.5 nM), saturability (Bmax = 171 +/- 21 fmol/mg protein), stereo-specificity, and rank order of potency expected of a specific alpha 2-receptor label when used as a reversible ligand in the rat cerebral cortex. The pharmacologic profile of AZC was similar to p-aminoclonidine (PAC), an established alpha 2-adrenoceptor partial agonist. Membranes covalently prelabeled with nonradioactive AZC showed a dose dependent decrease in the number of alpha 2-receptor sites subsequently detected by [3H]PAC and [3H]yohimbine. Specific covalent [3H]AZC binding to rat cerebral cortical alpha 2-receptors represented 35 +/- 7% of the total [3H]AZC bound. These data indicate that AZC is a selective alpha 2-adrenoceptor photoaffinity label which may be useful in the identification and purification of the alpha 2-Adrenoceptor.
mesh_terms: D000345:Affinity Labels / Q000138:chemical synthesis*; D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism; D003000:Clonidine / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008566:Membranes / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D010777:Photochemistry; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000345:Affinity Labels; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; C016986:apraclonidine; C047734:4-azidoclonidine; D003000:Clonidine; D009638:Norepinephrine