Renal dopamine-1 receptor coupling with gs and gq/11 proteins in
spontaneously hypertensive rats.
Hussain, Tahir, and Mustafa F. Lokhandwala.
Institute for Cardiovascular Studies, College of Pharmacy,
University of Houston, Houston, TX 77204-5511 USA
APStracts 3:0216F, 1996.
Dopamine-1 (DA1) receptor transduces its signal via adenylyl cyclase
and phospholipase C in the renal proximal tubules 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 Gq/11.
Fenoldopam, a DA1 receptor agonist, produced a time and
concentration-dependent stimulation in [35S]GTP[gamma]S binding in
WKY rats. Fenoldopam-induced (10 [mu]M) stimulation was significantly
inhibited by a DA1 receptor antagonist, SCH 23390. Specific
antibodies against C-terminals of Gs[alpha] and Gq/11[alpha] produced
50-60% and 40-50% inhibition respectively, in fenoldopam stimulation
of [35S]GTP[gamma]S binding. Western analysis of basolateral
membranes with these antibodies revealed the presence of Gs[alpha]
(45 kDa) and Gq/11[alpha] (42 kDa). Fenoldopam stimulation of
[35S]GTP[gamma]S binding was significantly attenuated in SHR compared
to WKY rats. Parathyroid hormone stimulation of [35S]GTP[gamma]S
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 while
the density of 45 kDa band was not significantly different compared
to WKY rats. We provide the direct evidence showing the coupling of
DA1 receptor with Gq/11[alpha] and Gs[alpha] and propose that in
addition to a defect in the receptor-G-protein coupling, a reduced
amount of Gq/11[alpha] observed in the hypertensive animals may also
contribute to the diminished dopamine-induced inhibition of
Na&,K&-ATPase in SHR.
Received 15 August 1996; accepted in final form 14 November 1996.
APS Manuscript Number F237-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996