Acute effects of vasopressin-v2-receptor antagonist on kidney aqp2
expression and subcellular distribution.
Christensen, Birgitte M_nster, David Marples, Uffe Birk Jensen, J_rge
Fr_kiaer, David Sheikh-Hamad, Mark Knepper and S_ren Nielsen.
Department of Cell Biology, Institute of Anatomy; 2Department of
Clinical Physiology, Aarhus University Hospital and Institute of
Experimental Clinical Research; 3Institute of Human Genetics,
University of Aarhus; 4Department of Physiology, University of Leeds;
5Baylor College of Medicine, Department of Medicine, Nephrology
Section, Houston, Texas 77030; and 6Laboratory of Kidney and
Electrolyte Metabolism, National Heart, Lung and Blood Institute,
National Institutes of Health, Bethesda, Maryland 20892
APStracts 5:0098F, 1998.
The acute effect of treatment with the vasopressin V2-receptor
antagonist OPC31260 (OPC) on AQP2 distribution and expression in rat
kidney was examined. Immunofluorescence and semi-quantitative
immunoelectron microscopy revealed that 15 min and 30 min of OPC
-treatment resulted in significant reduction in apical plasma membrane
labeling of AQP2, with a concomitant increase in labeling of vesicles
and multivesicular bodies. In parallel, OPC treatment induced a large
increase in urine output (0.6 [angstrom]a 0.2 v.s. 8.3 [angstrom]a
1.0 ml/hour (n=4)). Northern blotting using a 32P-labeled AQP2 cDNA
probe and a digoxigenin-labeled AQP2 RNA probe revealed a band of
approximately 1.6 kb corresponding to the predicted size of AQP2
mRNA. In control experiments thirsting increased, while water-loading
decreased AQP2 mRNA levels. Treatment of rats with OPC caused a
significant reduction in AQP2 mRNA within 30 min (52 [angstrom]a 21
%, n=8, p<0.025) and 60 min (56 [angstrom]a 7 %, n=4, p<0.001) of
treatment compared to i.v. saline injected controls. Thus, a very
rapid reduction in AQP2 mRNA was observed in response to vasopressin
-receptor antagonist treatment. The reduction in AQP2 mRNA persisted
after 24 hours (40 [angstrom]a 17 %, n=5, p<0.05) of OPC treatment.
There was a parallel increase in diuresis and reduction in urine
osmolality. In conclusion, V2-receptor blockade produced a rapid
internalization of AQP2 in parallel with a rapid increase in urine
output. Furthermore, OPC-treatment caused a rapid and significant
reduction in AQP2 mRNA expression, demonstrating that for rapid
regulation of AQP2 expression, modulation of AQP2 mRNA levels is
regulated via vasopressin-receptor signaling pathways.
Received 24 September 1997; accepted in final form 7 May 1998.
APS Manuscript Number F311-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 16 June 1998