Potassium permeability in the absence of fluid reabsorption in the
proximal tubule of the anaesthetized rat.
Wilson, Rod W., Mark Wareing, Jon Kibble, and Roger Green.
School of Biological Sciences, G.38, Stopford Building, University
of Manchester, Oxford Road, Manchester M13 9PT, UK. Department of
Biological Sciences, Hatherly Laboratories, University of Exeter,
Prince of Wales Road, Exeter EX4 4PS. Department of Biomedical
Science,University of Sheffield, Western Bank, Sheffield S10 2TN
APStracts 5:0057F, 1998.
A luminal microperfusion technique was used to examine the K+
permeability of surface proximal convoluted tubules in the kidney of
anaesthetized rats. Transtubular [K+] gradients were varied by
altering the concentration of KCl in luminal perfusates, to which
32mmol.l-1 of the impermeant solute raffinose was also added to
prevent net fluid reabsorption. The arithmetic mean transtubular [K+]
gradient was highly predictive of net potassium flux, yielding an
apparent K+ permeability of 31.9 +/- 1.7x10-5 cm.s-1 in the absence
of fluid reabsorption. When compared using identical calculation
techniques this was not significantly different from the permeability
derived in a previous study when fluid reabsorption was present
(Kibble et al., 1995, Am. J. Physiol., 268: F778-F783). We conclude
that fluid reabsorption does not affect the apparent permeability of
the proximal tubule to potassium. The apparent permeability to 86Rb,
measured following its addition to luminal perfusates, was not
significantly different from the value obtained for K+, suggesting
that rubidium is a useful marker for net potassium movements in the
PCT of the rat.
Received 1 August 1997; accepted in final form 23 February 1998.
APS Manuscript Number F258-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 9 March 1998