title: Renal dopamine DA1 receptor coupling with G(S) and G(q/11) proteins in spontaneously hypertensive rats.
abstract: The dopamine DA1 receptor transduces its signal via adenylyl cyclase and phospholipase C in the renal proximal tubule, which has been suggested to be defective at the level of receptor-G protein coupling in spontaneously hypertensive rats (SHR). We prepared basolateral membranes from Wistar-Kyoto (WKY) rats and SHR to determine the coupling of DA1 receptor with G proteins, especially G(q/11). Fenoldopam, a DA1-receptor agonist, produced a time- and concentration-dependent stimulation in 35S-labeled guanosine 5'-O-(3-thiotriphosphate) ([35S]GTPgammaS) binding in WKY rats. Fenoldopam-induced (10 microM) stimulation was significantly inhibited by a DA1-receptor antagonist, Sch-23390. Specific antibodies against COOH terminals of G(S)alpha and G(q/11)alpha produced 50-60% and 40-50% inhibition, respectively, in fenoldopam stimulation of [35S]GTPgammaS binding. Western analysis of basolateral membranes with these antibodies revealed the presence of G(S)alpha (45 kDa) and G(q/11)alpha (42 kDa). Fenoldopam stimulation of [35S]GTPgammaS binding was significantly attenuated in SHR compared with WKY rats. Parathyroid hormone stimulation of [35S]GTPgammaS binding was similar in SHR and WKY rats, whereas stimulation by phenylephrine was significantly reduced in SHR. Densitometric quantification of 42-kDa band showed a reduced amount in SHR, whereas the density of 45-kDa band was not significantly different compared with WKY rats. We provide the direct evidence showing the coupling of DA1 receptor with G(q/11)alpha and G(S)alpha and propose that, in addition to a defect in the receptor-G protein coupling, a reduced amount of G(q/11)alpha observed in the hypertensive animals may also contribute to the diminished dopamine-induced inhibition of Na+-K+-adenosinetriphosphatase in SHR.
authors.affiliation: Institute for Cardiovascular Studies, College of Pharmacy, University of Houston, Texas 77204-5511, USA.
authors.forename: T
authors.initials: T
authors.lastname: Hussain
authors.forename: M F
authors.initials: MF
authors.lastname: Lokhandwala
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000906:Antibodies; D001552:Benzazepines / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D018818:Fenoldopam / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D007668:Kidney / Q000502:physiology* / Q000503:physiopathology; D007700:Kinetics; D008297:Male; D010281:Parathyroid Hormone / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017447:Receptors, Dopamine D1 / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000906:Antibodies; D001552:Benzazepines; D010281:Parathyroid Hormone; D017447:Receptors, Dopamine D1; D010656:Phenylephrine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019204:GTP-Binding Proteins; D018818:Fenoldopam