title: Differences in photoaffinity labeling of DA1 receptors in renal proximal tubules from normotensive rat and SHR.
abstract: Renal DA1 dopamine receptors in proximal tubule membranes of normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) were characterized with the novel D1 dopamine receptor-selective photoaffinity probe, (+/-)-7-[125I]iodo-8-hydroxy-3-methyl-1-(4-azidophenyl)-2,3,4,5- tetrahydro-1H-3-benzazepine ([125I]MAB). Under nonphotolyzing conditions, saturation studies showed that [125I]MAB bound with similar affinity to DA1 dopamine receptors in both WKY [dissociation constant (Kd) = 16.3 nM] and SHR (Kd = 19.5 nM). At photolysis, [125I]MAB was irreversibly incorporated into a single major protein of 74,000 Da in both WKY and SHR. DA1-selective antagonists blocked photolabeling of DA1 sites with similar efficiency and specificity in SHR and WKY. However, under identical assay conditions, dopaminergic agonists were unable to block photoincorporation of [125I]MAB in SHR but not in WKY. This pattern of labeling of DA1 sites by [125I]MAB may suggest the presence of defective agonist, but not antagonist, binding domains on the receptor in SHR but not in WKY rats.
authors.affiliation: Department of Pediatrics, Georgetown University Children's Medical Center, Georgetown University, Washington, District of Columbia 20007, USA.
authors.forename: P
authors.initials: P
authors.lastname: Vachvanichsanong
authors.forename: K
authors.initials: K
authors.lastname: Kimura
authors.forename: A
authors.initials: A
authors.lastname: Sidhu
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001345:Autoradiography; D001386:Azides / Q000378:metabolism*; D001552:Benzazepines / Q000378:metabolism*; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D007457:Iodine Radioisotopes; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D007700:Kinetics; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017447:Receptors, Dopamine D1 / Q000302:isolation & purification / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D000345:Affinity Labels; D001386:Azides; D001552:Benzazepines; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D007457:Iodine Radioisotopes; D017447:Receptors, Dopamine D1; C058320:7-iodo-8-hydroxy-3-methyl-1-(4-azidophenyl)-2,3,4,5-tetrahydro-1H-3-benzazepine