SODIUM-DEPENDENT AND SODIUM-INDEPENDENT TRANSPORT OF L-GLUTAMATE IN THE RAT INTESTINAL CRYPT-LIKE CELL-LINE IEC-17

Mechanisms of L-glutamate transport in intestinal crypts were investig ated using the rat intestinal crypt-like cell line IEC-17. Kinetic ana lysis and competition experiments run in the presence or in the absenc e of extracellular sodium indicate that L-glutamate uptake occurs thro ugh three different transport components: (1) a high affinity Na+-inde pendent component also carrying cystine, similar to system x(C)(-); (2 ) a high affinity Na+-dependent component inhibited by D- and L-aspart ate corresponding to the ubiquitous system X-A,G(-); and (3) a low aff inity Na+-dependent system resembling the neutral amino acid transport system ASC. The simultaneous presence of these three components sugge st that crypt cells are ready to face potential high variations of L-g lutamate concentration in the intestinal villus environment. (C) 1997 Academic Press.