Inhibition of basolateral potassium conductance by taurine in the
proximal convoluted tubule.
Breton, Sylvie, Fouzia Belachgar, Mireille Marsolais, Jean-Yves
Lapointe, and Raynald Laprade.
Groupe de recherche en transport membranaire, Universit[acute]e de
Montr[acute]eal, C.P. 6128, Succursale A, Montr[acute]eal,
Qu[acute]ebec, Canada, H3C 3J7
APStracts 3:0139F, 1996.
The effect of taurine on the electrophysiological properties of the
basolateral membrane of the rabbit proximal convoluted tubule was
examined. Short duration isosmotic pulses of 40 mM taurine in the
bath solution induced basolateral membrane depolarizations (_Vbl) of
6.44 +/- 0.5 mV, which were reduced by 58% in absence of Na+. In
presence of barium and quinine, _Vbl were reduced by 55% in Na+
-containing bath solutions and were completely abolished in Na+-free
solutions. Continuous addition of taurine into the bath solutions for
a period of 5 min induced: 1) a decrease in the partial conductance
of the basolateral membrane to K+ (tK) from 0.39 to 0.23; 2) an
increase in the partial conductance to Cl- (tCl) from 0.055 to 0.172;
3) a rapid and transient increase of the partial conductance mediated
by the Na-HCO3 cotransporter (tNaHCO3) from 0.37 to 0.52, followed by
a progressive decrease to 0.29; and 4) a depolarization of the
basolateral membrane of 16 mV. The membrane absolute conductance
mediated by the Na-HCO3 cotransporter was not initially affected by
taurine, whereas that to K (GK) initially decreased by a maximal
factor of 2 after 1 min, followed by a partial recovery after 5 min,
and that to Cl (GCl) increased by a factor of 4. Addition of taurine
after a hypotonicity-induced cell swelling produced an inhibition of
GK comparable to the one observed under isotonic conditions. These
results demonstrate the presence of an electrogenic Na-dependent
transport of taurine, and indicate that taurine inhibits GK.
Received 7 May 1996; accepted in final form 25 July 1996.
APS Manuscript Number F136-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 21 August 1996