Amino acid and hexose transport by cultured crypt cells from rat small intestine.

The characteristics of amino acid and sugar transport in intestinal crypt epithelial cells have been examined by measuring substrate uptake in an established epithelial cell line. These cells (IEC-6 cells) have been characterized as derived from rat small intestinal crypt cells on the basis of morphological criteria (J. Cell. Biol. 80: 248-265, 1979). Amino acid transport appeared to be mediated by both Na+-dependent and Na+-independent systems. Hexose uptake was stereospecific and Na+ independent, and was markedly inhibited by phloretin and cytochalasin B. Since glucocorticoids are known to have profound effects on maturation of the intestinal epithelium in vivo, their effects on transport properties of the cultured crypt cells were studied. Hydrocortisone, while completely inhibiting cell growth, increased the initial uptake rates of various hexoses, while having little or nor effect on the initial rate of amino acid uptake. The increased hexose uptake appeared to be due to a change in Vmax rather than Km. Appearance of the Na+-dependent hexose transport system, which is present in differentiated enterocytes, was not elicited by in vitro treatment with glucocortcoids.