AJP - Gastrointestinal and Liver Physiology, Vol 242, Issue 3 209-G214, Copyright © 1982 by American Physiological Society
Demonstration of net potassium absorption in mammalian colon
J. P. Hayslett, J. Halevy, P. E. Pace and H. J. Binder
The present in vivo studies were performed in the rat to determine whether
the colon was capable of net potassium absorption, as well as secretion,
and to further elucidate the process responsible for net potassium
movement. Both the proximal and distal lumina of the colon of control,
potassium-deficient, and potassium-loaded animals were perfused with
solutions containing either 140 or 20 mmol/l sodium. Net potassium
secretion was present in both proximal and distal colon of control animals
during perfusion with the 140 mmol/l sodium solution. The rate of net
potassium secretion was reduced in the potassium-deficient animals. During
perfusion with the 20 mmol/l sodium solution, the rate of potassium
secretion was also reduced (compared with control perfusion solution) in
both the control and potassium-deficient animals. As a result, there was
net potassium absorption (0.94 +/- 0.14 mueq.1-1.g dry wt-1) and zero net
potassium movement in the distal and proximal segments, respectively, of
the potassium-deficient animals perfused with the low-sodium solution.
Additional studies were performed to determine whether net potassium
secretion was saturable and showed that, during progressive increases in
the plasma potassium level, net secretion was constant at plasma potassium
levels above 11-13 meq/l. These data, therefore, demonstrate that the
mammalian colon regulates intestinal transport of potassium by both
absorptive and secretory mechanisms and that a carrier-mediated process
probably regulates both transport processes.
