AJP - Gastrointestinal and Liver Physiology, Vol 244, Issue 1 33-G39, Copyright © 1983 by American Physiological Society
Anion effects on fluid absorption from rat jejunum perfused in vivo
M. H. Humphreys and L. Y. Chou
Perfusion of rat jejunal segments in vivo with an isotonic, HCO3-free
SO4-Ringer solution resulted in low rates of net sodium (JNanet) and water
absorption. When the perfusion fluid was changed to one containing 25 mM
Na2SO3, JNanet increased from 4.7 +/- 1.2 to 11.6 +/- 1.5 (SE) mumol X cm-1
X h-1 (P less than 0.001). This increased absorption was accompanied by
comparable increases in chloride and water absorption, occurred without a
detectable change in potential difference across the perfused segment, and
was readily reversed on reinstitution of perfusion with SO4-Ringer.
Perfusion with SO3-Ringer had no effect on electrolyte absorption from
terminal segments of rat ileum. Addition of L-phenylalanine stimulated
absorption from SO4-Ringer perfusate but not from SO3-Ringer perfusate.
Addition of 25 mM NaHCO3 to SO4-Ringer perfusate caused parallel increases
in JNanet and JHCO3net; when 25 mM NaHCO3 was added to SO4-Ringer perfusate
that also contained 25 mM NaSCN, the same increase in JHCO3net occurred but
was not associated with any increase in JNanet. These results indicate a
potent effect of SO2-3 and HCO-3 to stimulate JNanet from rat jejunum but
not from ileum. These anion effects on intestinal transport in vivo
resemble their effects on ATPase activity of brush-border fractions from
small intestine in vitro and raise the possibility that these effects on
ion transport could be mediated through the changes in brush-border ATPase
activity, which are brought about by exposure to these anions, although
other explanations are also possible.
