TY - JOUR T1 - Role of G<sub>αq</sub> or G<sub>αo</sub> Proteins in α<sub>1</sub>-Adrenoceptor Subtype-Mediated Responses in Fischer 344 Rat Aorta JF - Molecular Pharmacology JO - Mol Pharmacol SP - 1064 LP - 1070 DO - 10.1124/mol.52.6.1064 VL - 52 IS - 6 AU - Hakan Gurdal AU - Tammy M. Seasholtz AU - Hoau-Yan Wang AU - R. Dale Brown AU - Mark D. Johnson AU - Eitan Friedman Y1 - 1997/12/01 UR - http://molpharm.aspetjournals.org/content/52/6/1064.abstract N2 - Previous studies showed that α-adrenoceptor (AR) stimulation with norepinephrine is more potent at eliciting contraction in aortas from 1-month-old Fischer 344 rats than from older rats and that this response is mediated by α1b- and α1d-AR subtypes in 1-month-old rats. We examined the G proteins responsible for α1-AR-mediated contractile response and inositol phosphate accumulation in the aortas of 1-month-old Fischer 344 rats. Pertussis toxin (PTX) treatment (2.5 μg/ml for 4 hr) of aortic rings partially inhibited phenylephrine (PHE)-stimulated contraction and inositol phosphate accumulation, suggesting the involvement of PTX-sensitive and -insensitive G proteins. Specific antisera directed against Gαq and Gαo but not Gαs and Gαi precipitated specific α1-AR binding sites labeled with 2-[β-(4-hydroxy-3-[125I]iodophenyl)ethylaminomethyl]tetralone. The number of 2-[β-(4-hydroxy-3-[125I]iodophenyl)ethylaminomethyl]tetralone binding sites precipitated by Gα proteins was increased by activating membrane α1-ARs with PHE. Moreover, PHE stimulated the palmitoylation of Gαq and Gαo, and this response was blocked by the α1-AR antagonist prazosin. Characterization of the α1-AR subtypes that couple to G proteins indicates that although aortic α1a-, α1b-, and α1d-ARs were associated with Gαq, α1b-AR was also linked to Gαo. These results suggest that α1-ARs mediate the contractile response in rat aorta by coupling to both Gq protein and the PTX-sensitive Go protein. ER -