Absence of da-1/da-2 dopamine receptor interactions in proximal
tubules of spontaneously hypertensive rats.
Vachvanichsanong, Prayong, Shifra Sela, and Anita Sidhu.
Department of Pediatrics, Georgetown University Children's Medical
Center, Georgetown University, Washington D.C. 20007
APStracts 2:0116F, 1995.
The impact of defective DA-1 dopamine (DA) receptors in proximal
tubules (PT) of the spontaneously hypertensive rat (SHR), on DA-1/DA
-2 receptor interactions, was assessed with the DA-1-selective
photoaffinity ligand, [125I]MAB. In PT membranes from both
normotensive rats (WKY) and SHR, [125I]MAB was specifically
incorporated into a polypeptide with Mr of 74,000 daltons,
corresponding to the DA-1 receptor. The labeling of this band by
[125I]MAB in both SHR and WKY was not prevented by SKF 82526, a
potent DA-1-selective agonist. However, in the presence of the DA-2
antagonist, (-)sulpiride, but not DA-2 agonist, LY 171555, SKF 82526
abolished photoincorporation of [125I]MAB into the 74,000 dalton band
in WKY. In SHR, (-)sulpiride failed to enhance the ability of SKF
82526 to compete with [125I]MAB for binding to the 74,000 dalton
subunit. In competition binding studies with SKF 82526, (-)sulpiride
induced the formation of agonist high-affinity binding sites in WKY,
but not in SHR. These data suggest that in membranes of SHR, but not
WKY, DA-1/DA-2 DA receptor interactions are lacking.
Received 26 April 1995; accepted in final form 10 July 1995.
APS Manuscript Number F136-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.