Na/d-glucose cotransport in renal brush-border membrane vesicles of
an early teleost (oncorhynchus mykiss).
Freire, C. A., E. Kinne-Saffran, K. W. Beyenbach,and R. K. H. Kinne.
Max-Planck-Institut fur molekulare Physiologie, Abteilung
Epithelphysiologie, Rheinlanddamm 201, 44139 Dortmund, Germany; AND
Section of Physiology, Veterinary Research Tower T9-026, Cornell
University, Ithaca, New York 14853
APStracts 2:0075R, 1995.
Brush-border membrane vesicles (BBMV), enriched with alkaline
phosphatase (8.1-fold) and [gamma]-glutamyl transpeptidase (11.5
-fold), were prepared from the rainbow trout kidney. 3H-D-glucose
uptake was stimulated by inward Na gradients, but not by K, choline,
Li, N-methyl-glucamine, or mannitol gradients. Na-dependent glucose
uptake displayed overshoot in voltage-polarized vesicles (VPV,
negative inside), but not in short-circuited vesicles (SCV).
Recognition of carbons 2-3 of the glucopyranose ring was essential
for glucose uptake. Phlorizin inhibited Na-dependent D-glucose uptake
with a Ki of 11.4 [mu]M. The Km(glucose) was 0.58 mM in VPV and
increased to 1.49 mM in SCV. Km(Na) was 193 mM in VPV and similar in
SCV. Vmax(Na) was reduced in SCV. The Hill coefficient was 1 for both
Na and glucose in VPV and SCV. Our studies indicate a single Na/D
-glucose cotransporter which transports Na and glucose with a 1:1
stoichiometry and voltage-dependent kinetics. The transporter shares
functional properties with both mammalian transporters, SGLT1 and
SGLT2.
Received 19 December 1994; accepted in final form 28 February
1995.
APS Manuscript Number R717-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 April 1995.