Galactose transport in rabbit ileum

Summary

The four unidirectional fluxes of galactose across the mucosal and serosal borders of rabbit ileum have been evaluated as functions of galactose concentration on a single piece of tissue from simultaneous measurements of mucosal-to-serosal and serosal-to-mucosal fluxes using¹⁴C- and³H-galactose and the steady-state ratio of the two isotopes in the tissue. The effects of Na removal, ouabain and a hypertonic serosal solution on these fluxes was investigated. Galactose was actively transported across the mucosal membrane under control conditions; this process was inhibited by Na removal and ouabain as a result of a decrease in flux from mucosal solution to cell and an increase in flux in the opposite direction. Effective galactose permeability of the serosal membrane was comparable to that of the mucosal membrane. Galactose transfer across the serosal membrane did not appear to conform to simple diffusion and may involve a facilitated transfer mechanism although a weak active transport from serosal solution to cell cannot be ruled out. Galactose movement at the serosal side of the cell was not influenced by Na.