AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 2 249-G252, Copyright © 1986 by American Physiological Society
Sodium and chloride transport in the large intestine of potassium-loaded rats
M. E. Budinger, E. S. Foster, J. P. Hayslett and H. J. Binder
Increased dietary potassium ("potassium loading") induces several adaptive
changes in colonic function, including increased potential-dependent
potassium secretion, active potassium secretion, and Na-K-ATPase activity,
but does not alter net sodium absorption in vivo. To establish whether
potassium loading stimulates active sodium transport, unidirectional, net
sodium, and chloride fluxes were determined under voltage-clamp conditions
across isolated rat distal colonic mucosa. In normal animals net sodium
flux (JNanet), net chloride flux (JClnet) and short-circuit current (Isc)
were 6.1 +/- 1.1, 8.4 +/- 1.0, and 0.7 +/- 0.1 mu eq X h-1. cm-2,
respectively; potassium loading significantly increased JNanet and Isc by
4.9 +/- 1.4 and 3.5 +/- 0.7 mu eq X h-1 X cm-2, respectively, without
changing JClnet. Amiloride (0.1 mM) inhibited the increases in JNanet and
Isc produced by potassium loading. In Cl-free Ringer solution in normal
animals JNanet was reduced to 0.6 +/- 0.3 mu eq X h-1 X cm-2. Potassium
loading produced identical increases in JNanet and Isc, which were also
completely inhibited by 0.1 mM amiloride. These studies establish that
potassium loading induces amiloride-sensitive electrogenic sodium
absorption without affecting electroneutral sodium-chloride absorption.
