title: Identification of the subunit structure of rat pineal adrenergic receptors by photoaffinity labeling.
abstract: The adrenergic receptors of rat pineal gland were investigated using radiolabeled ligand binding and photoaffinity labeling techniques. 125I-2-[beta-(4-hydroxyphenyl)ethylaminomethyl]tetralone (125I-HEAT) and 125I-cyanopindolol (125I-CYP) labeled specific sites on rat pineal gland membranes with equilibrium dissociation constants (KD) of 48 (+/- 5) pM and 30 (+/- 5) pM, respectively. Binding site maxima were 481 (+/- 63) and 1,020 (+/- 85) fmol/mg protein. The sites labeled by 125I-HEAT had the pharmacological characteristics of alpha 1-adrenergic receptors. 125I-CYP-labeled beta-adrenergic receptors were characterized as a homogeneous population of beta 1-adrenergic receptors. The alpha 1- and beta 1-adrenergic receptors were covalently labeled with the specific photoaffinity probes 4-amino-6,7-dimethoxy-2-(4-[5-(4-azido-3-[125I]iodophenyl) pentanoyl]-1-piperazinyl) quinazoline (125I-APDQ) and 125I-p-azidobenzylcarazolol (125I-pABC). 125I-APDQ labeled an alpha 1-adrenergic receptor peptide of Mr = 74,000 (+/- 4,000), which was similar to peptides labeled in rat cerebral cortex, liver, and spleen. 125I-pABC labeled a single beta 1-adrenergic receptor peptide with a Mr = 42,000 (+/- 1,500), which differed from the 60-65,000 peptide commonly seen in mammalian tissues. Possible reasons for these differences are discussed.
mesh_terms: D000345:Affinity Labels / Q000378:metabolism*; D000818:Animals; D001386:Azides / Q000378:metabolism; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008970:Molecular Weight; D010627:Phenethylamines / Q000378:metabolism; D010777:Photochemistry; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D010870:Pineal Gland / Q000378:metabolism*; D011412:Propanolamines / Q000378:metabolism; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013154:Spleen / Q000378:metabolism; D044024:Tetralones
chemical_list: D000345:Affinity Labels; D001386:Azides; D010627:Phenethylamines; D011412:Propanolamines; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D044024:Tetralones; C010652:BE 2254; C047975:cyanopindolol; C032509:4-azidobenzylcarazolol; C039335:4-amino-6,7-dimethoxy-2-(4-(5-(3-iodo-4-azidophenyl)pentanoyl)-1-piperazinyl)quinazoline; D010869:Pindolol