Dopamine d4 receptor isoform mrna and protein is expressed in the
rat cortical collecting duct.
Sun, Duo, Teresa W. Wilborn, and James A. Schafer.
Departments of Physiology and Biophysics, Nephrology Research and
Training Center, University of Alabama at Birmingham, Birmingham, AL
35294
APStracts 5:0132F, 1998.
We reported previously (Am. J. Physiol. 271 [Renal Fluid Electrolyte
Physiol. 40]: F391-F400, 1996) that dopamine inhibits vasopressin
(AVP)-dependent water permeability and Na+ transport in the rat
cortical collecting duct (CCD) apparently through a D4 dopamine
receptor. The present experiments used RT-PCR of total RNA extracted
from microdissected rat CCD to determine if the D4 and D1A dopamine
receptor isoforms are expressed. Specific primers were used to
amplify three regions of the D4 cDNA. All three gave products with 98
to 100% nucleotide identity to the known rat D4 sequence; however,
there was an extra six base-pair insert at the 3' end of the second
transmembrane region that was identical to the human and mouse but
which had not been documented in the rat sequence. D4 receptor
protein was also localized exclusively to the CCD and medullary
collecting ducts by immunohistochemistry. Two regions of the D1A
dopamine receptor message were also amplified by RT-PCR of RNA from
rat CCD and were verified by sequencing and immunohistochemistry. We
conclude that both D4 and D1A dopamine receptors are expressed in the
rat CCD, but the physiological effects are attributable to a D4
receptor.
Received 25 June 1997; accepted in final form 22 July 1998.
APS Manuscript Number F208-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 21 September 1998