Ouabain Effect on Transmural Transport of Potassium by Canine Small Intestine. ∗

Summary

Evidence of the alteration of the unidirectional, mucosa to serosa, trans-mural potassium flux by ouabain has been presented. This evidence suggests several conclusions concerning the transport of potassium by the small intestinal mucosal cell. It seems likely that potassium actually passes through the cell, rather than passing through extracellular channels between cells as is commonly suggested. This alteration in cellular potassium transport would appear to be carrier linked, and the carrier involved in the ouabain-enhanced transmural flux is on the serosal surface of the mucosal cell. Because potassium cannot be shown to be transported against an electrochemical gradient, and potassium transport has a low Q₁₀ suggestive of a diffusion process, the carrier process involved in potassium transport may be an example of an equilibrating carrier system. Whether potassium has a carrier mechanism regularly available, or whether it is able to use the sodium carrier when the latter is altered by the addition of ouabain to the system is an important question which