K+ transport by rat colon: adaptation to a low potassium diet
Tannen, R.L.; Marino, R.; Dawson, D.C.
American Journal of Physiology 250(3 Pt 2): F483-F487
1986
ISSN/ISBN: 0002-9513 PMID: 3953826 Document Number: 277057
Transmural 86Rb fluxes across sheets of distal colonic epithelium from rats were estimated under short-circuit conditions. Preliminary studies using a double-isotope method demonstrated that 86Rb and 42K fluxes were similar; therefore 86Rb flux was considered equivalent to potassium+ flux. The distal half of the colon from each rat was divided into 2 segments, referred to as early and late distal colon. Experiments were made using rats fed on a K+-free, control (0.15 mmol/g) and high-K+ (1.13 mmol/g) powdered diet of otherwise identical electrolyte content. Net K+ secretion (Jnet) by the early distal colon was reduced from 0.45 in the controls to -0.02 mu Eq/cmsuperscript 2 h by a low-K+ diet as a result of a decrease in serosal-to-mucosal flux (Jsm), with no change in mucosal-to-serosal flux. Conductance and short-circuit current were unchanged. Jnet by the late distal colon was 0.17 in the controls and 0.01 mu Eq/cmsuperscript 2 h with a low-K+ diet, but this difference was not significant. In comparison with the controls, a high-K+ diet had no effect on Jnet by the early distal colon (0.48 mu Eq/cmsuperscript 2 h) but increased Jnet by the late distal colon (0.77 mu Eq/cmsuperscript 2 h), due entirely to an increase in Jsm.