Endogenous angiotensin ii modulates rat proximal tubule transport
with acute changes in extracellular volume.
Quan, Albert, and Michel Baum.
Departments of Pediatrics, and Internal Medicine, University of
Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235
-9063
APStracts 5:0069F, 1998.
In the present study, we examined if the effect of endogenously
produced angiotensin II on proximal tubule transport in the male
Sprague-Dawley rat is regulated by acute changes in extracellular
volume. We measured the magnitude of endogenous angiotensin II
mediated stimulation of transport by sequentially perfusing proximal
tubules in vivo, first with an ultrafiltrate like solution followed
by reperfusion of the same tubule with an ultrafiltrate like solution
containing 10-8 M losartan (angiotensin II receptor antagonist).
During volume contraction, 10-8 M losartan decreased volume
reabsorption from 4.20(0.50 nl/mm(min to 1.70(0.30 nl/mm(min,
p<0.05, a decrease of 58.0(7.0%. In contrast, after acute volume
expansion, 10-8 M losartan decreased volume reabsorption from
1.84(0.20 nl/mm(min to 1.31(0.20 nl/mm(min, p<0.05, a decrease of
29.6(9.0%. In hydropenic rats, addition of exogenous luminal
angiotensin II had no effect on transport. However, in volume
expanded rats, addition of 10-8 M angiotensin II, increased volume
reabsorption from 2.10(0.34 nl/mm(min to 4.38(0.59 nl/mm(min,
p<0.005. These data are consistent with endogenously produced
angiotensin II augmenting proximal tubule transport to a greater
degree during volume contraction than after volume expansion.
Received 22 July 1997; accepted in final form 6 March 1998.
APS Manuscript Number F238-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 6 April 1998