AJP - Cell Physiology, Vol 255, Issue 1 C95-101, Copyright © 1988 by American Physiological Society
Effect of Na+ on intestinal succinate transport and metabolism in vitro
A. J. Moe, R. T. Mallet, M. J. Jackson, J. A. Hollywood and J. K. Kelleher
George Washington University Medical Center, Washington, DC 20037.
The effect of Na+ on 14CO2 production from [14C]succinate was studied in
isolated rat enterocytes, and Na+-dependent succinate transport was
characterized in pig intestinal brush-border membrane vesicles. The
production of 14CO2 from [14C]succinate by enterocytes was decreased
12-fold when Na+ was replaced by N-methyl-D-glucamine in the absence of
glutamine and 20-fold in the presence of 0.2 or 0.5 mM glutamine. The ratio
of 14CO2 produced from [1,4-14C]succinate to that produced by
[2,3-14C]succinate was not affected by Na+ replacement, indicating that the
pattern of tricarboxylic acid cycle metabolism was not altered. The uptake
of [14C]succinate by brush-border membrane vesicles was stimulated 10-fold
in the presence of 100 mM NaCl compared with 100 mM KCl. When succinate
uptake was corrected to transport into an osmotically sensitive space, the
magnitude of the Na+ stimulation was 20-fold. Succinate transport into
brush-border membrane vesicles was Na+ dependent, electroneutral,
nonconcentrative, with an apparent Na+-succinate coupling ratio of 2:1.
Results of this study indicate that Na+-stimulated CO2 production by
enterocytes can be explained by the effect of Na+ on succinate transport
across the brush-border membrane.
