Taurine reabsorption by a carrier interacting with furosemide in
short and long henle's loops of rat nephrons.
Silbernagl, Stefan, Katharina V[diaeresis]olker, Hans-J. Lang, and
William H. Dantzler.
Physiologisches Institut der Universit[umlaut]at W[umlaut]urzburg,
D-97070 W[umlaut]urzburg, Germany; Hoechst AG, D-65926 Frankfurt/M,
Germany; and Department of Physiology, College of Medicine,
University of Arizona, Tucson, AZ 85724-5051
APStracts 3:0191F, 1996.
Taurine is net-reabsorbed in the proximal convolution by Cl-
-stimulated Na+-symport specific for [beta]-amino acids, but not in
later nephron segments However, large unidirectional taurine
transport takes place there. To investigate unidirectional taurine
reabsorption, we co-microinfused 3H-taurine and 14C-inulin into late
proximal (LP), early distal (ED), and late distal (LD) tubule
segments, as well as into the tips of long loops of Henle (LLH) of
rats in vivo, and determined fractional reabsorption of 3H-taurine
(FR) in the ipsilateral urine. FR (9 [mu]mol/l taurine) was 80 to 93
(LP), 16 (ED) and 8 % (LD). At 26 mmol/l taurine, FR decreased to 13
(LP) and 6 % (ED). FR also decreased when Na+ or Cl- was absent or
furosemide (5 x 10-5 mol/l) was added. Bumetanide (5 x 10-5 mol/l)
had no effect, whereas aniline-2-sulfonic acid (ASA) inhibited.
During LLH microinfusion, FR was 55% at 66 and 17% at 228 [mu]mol/l
and was again inhibited by furosemide and ASA, but not by bumetanide.
14 C-t aurine reabsorption from microperfused proximal convolutions
was not influenced by furosemide. Chronic water diuresis did not
affect taurine reabsorption in short Henle's loops. We conclude, that
taurine can enter cells of the distal nephron from the lumen by a
Na+- and partly Cl- -dependent carrier with which C[alpha], [beta]
-substituted taurine (ASA) and C[alpha], [beta]- and N-substituted
[beta]-alanine (furosemide) directly interact. Thus, proximal and
distal taurine carriers seem to be different.
Received 2 July 1996; accepted in final form 17 October 1996.
APS Manuscript Number F182-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996