The transport of alanine and glutamine into isolated rat intestinal epithelial cells.

(1) The transport of alanine and glutamine into isolated rat intestinal epithelial cells, prepared as described previously (Watford, M., Lund, P. and Krebs, H.A. (1979) Biochem. J. 178, 589-596), was studied. (2) Cells isolated by this method accumulated alanine 7-fold from an external concentration of 0.5 mM, and by this criterion appear more suitable for transport studies than do previous rat intestinal cell preparations. (3) In these cells, it was shown using several different approaches that the major part of the transport of alanine and glutamine is mediated by a common carrier which is Na+ dependent and is sensitive to inhibition by 2-methylaminoisobutyric acid. (4) These results are in contrast to the situation in isolated hepatocytes were glutamine is transported by a carrier system (System N) distinct from that that which mediates the transport of alanine. (5) It is suggested that a major metabolic function of this transport system in intestinal cells is the exchange of extracellular glutamine for intracellular alanine, which is a major product of glutamine metabolism in the gut.