FIGURE 5.

Comprehensive substrate profile of glutamate transporters. Oocytes were injected with 5 ng of cRNA for EAAT1 or remained un-injected for a 4-day expression period in OR2⁺ (pH 7.8). Amino acid accumulation was analyzed as fold-change relative to un-injected (U.I.) oocytes (A) or as absolute (Δ) change from U.I. oocytes (B) after a 4 h incubation in modified L-15 medium. The known specificity and stoichiometry of the transporters are shown as a cartoon. A more intense red for the same amino acid at 4 h indicates active accumulation. Pyro-glutamic acid (2-oxo-proline) and ornithine are included in all heat maps as they are known GC-MS derivatives of glutamate and arginine, respectively. The internal standard ribitol was also included in each heat-map as a negative control to indicate any deviation from fold-change of 1 ± 0.1 or 10% of the absolute value. * Indicates a difference in the means between the two time points at the p < 0.05 level using a paired t-test as calculated from the absolute mass spectrometer raw values. The figures are a representative example of 3 experiments with n = 12 transporter-expressing and un-injected oocytes per replicate.