Oxytocin as an antidiuretic hormone: ii. role of v2 vasopressin
receptor .
Chou, Chung-Lin, Susan R. Digiovanni, Andrew Luther, Stephen J.
Lolait, and Mark A. Knepper.
Laboratory of Kidney and Electrolyte Metabolism, National Heart,
Lung and Blood Institute and Laboratory of Cell Biology, National
Institute of Mental Health, National Institutes of Health, Bethesda,
MD 20892
APStracts 2:0035F, 1995.
We conducted this study to determine what receptor mediates the effect
of oxytocin to increase osmotic water permeability (Pf) in the rat
inner medullary collecting duct (IMCD). Reverse transcription
-polymerase chain reaction (RT-PCR) experiments demonstrated that mRNA
for both the oxytocin receptor and the V2 receptor is present in the
rat terminal IMCD. In isolated perfused IMCD segments, we found that
the V2 vasopressin receptor antagonist II-AVP ([d(CH2)5,D
-Ile2,Ile4Arg8]vasopressin), but not oxytocin receptor antagonists,
blocked the hydro-osmotic response to 200 pM oxytocin. The selective
oxytocin receptor agonist [Thr4,Gly7]oxytocin (TG-OXT) did not
increase water permeability. Oxytocin also increased urea
permeability in IMCD segments. Studies in IMCD suspensions showed
that oxytocin increases cyclic AMP production in a dose-dependent
fashion with a half-maximal (EC50) response at 5.2 nM. The dose
-response curves were virtually identical for IMCD suspensions from
Sprague-Dawley rats and Brattleboro rats. The oxytocin dose-response
curve was displaced to the right of the vasopressin dose-response
curve (EC50, 0.44 nM). From these results, we conclude that the V2
receptor mediates the hydro-osmotic action of oxytocin in rat inner
medullary collecting duct.
Received 20 December 1994; accepted in final form 20 February
1995.
APS Manuscript Number F452-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.