Regional time-dependent changes in vasopressin v2 receptor
expression in the rat kidney during water restriction.
Park, Frank, George Koike, and Allen W. Cowley, Jr.
Medical College of Wisconsin, Department of Physiology, Milwaukee,
WI
APStracts 5:0028F, 1998.
Elevations of arginine vasopressin (AVP) binding to renal vasopressin
V2 receptors (V2R) enhance water and urea reabsorption in the
collecting duct epithelium. This study was designed to quantify the
levels of V2R mRNA and protein within the distinct regions of the
Sprague Dawley rat kidney (i.e., the cortex, outer and inner medulla)
during 24 and 48 hours of water restriction. A competitive reverse
transcription-polymerase chain reaction (RT-PCR) assay was developed
to quantify changes in the V2R mRNA in which a deletion mutant RNA
transcript was used to control for the efficiency of RT-PCR. Western
blot analysis was utilized for the quantification of the V2R protein.
The results showed that the steady state levels of the V2R mRNA
decreased in a time-dependent manner in the cortex, outer medulla and
inner medulla throughout 48 hours of water restriction. _Western blot
analysis revealed that the V2R protein in the renal cortex decreased
after the initial 24 hours of water restriction and remained
decreased at 48 hours. In contrast, outer medullary V2R protein
decreased significantly only after 48 hours of water restriction
while no significant change in the inner medullary V2R protein was
observed throughout the 48 hours of water restriction. _These results
suggest that water restriction leads to a regional time-dependent
down-regulation of the V2R mRNA and protein within the rat kidney.
The stability of the plasma membrane V2R protein within the inner
medulla may allow for the optimization of urine concentration and
minimize water loss during periods of water restriction.
Received 13 November 1997; accepted in final form 22 January
1998.
APS Manuscript Number F357-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 28 January 1998