title: Persistent defective coupling of dopamine-1 receptors to G proteins after solubilization from kidney proximal tubules of hypertensive rats.
abstract: The natriuretic effect of dopamine-1 (DA-1) agonists is reduced in spontaneously hypertensive rat (SHR), partly because of defective DA-1 receptor-adenylate cyclase (AC) coupling in renal proximal convoluted tubules. To investigate this defective coupling, DA-1 dopamine receptors from renal proximal tubules were solubilized and reconstituted into phospholipid vesicles. The binding of DA-1-selective ligand [125I]SCH 23982 was specific and saturable, with no differences in receptor density or Kd between SHR and normotensive rats (Wistar-Kyoto rats; WKY). Competition experiments of the reconstituted DA-1 dopamine receptors in WKY with a DA-1-selective agonist, SKF R-38393, revealed the presence of high- (Kh = 350 +/- 209 nM) and low-affinity (Kl = 70,500 +/- 39,500 nM) binding sites. 100 microM Gpp(NH)p abolished the agonist high-affinity sites, converting them to a low-affinity state (Ki = 33,650 +/- 10,850 nM). In SHR, one affinity site was noted (Ki = 13,800 +/- 500) and was not modulated by Gpp(NH)p (Ki = 11,505 +/- 2,295). The absence of guanine nucleotide-sensitive agonist high-affinity sites may explain the defective DA-1/AC coupling mechanism in the SHR.
authors.affiliation: Department of Pediatrics, Georgetown University, Washington, DC 20007.
authors.forename: A
authors.initials: A
authors.lastname: Sidhu
authors.forename: P
authors.initials: P
authors.lastname: Vachvanichsanong
authors.forename: P A
authors.initials: PA
authors.lastname: Jose
authors.forename: R A
authors.initials: RA
authors.lastname: Felder
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000031:analogs & derivatives / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006973:Hypertension / Q000378:metabolism*; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D011954:Receptors, Dopamine / Q000378:metabolism*; D017447:Receptors, Dopamine D1; D012995:Solubility
chemical_list: C049558:8-iodo-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepine-7-ol; D001552:Benzazepines; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D006165:Guanylyl Imidodiphosphate; D019204:GTP-Binding Proteins