Fig 7.

Homo- and hetero-exchange of intracellular [³H]D-serine with extracellular test substrates in oocytes injected with human cRNA encoding SLC1A4 (A) or SLC1A5 (B). Ooctytes were pre-incubated with 100nM [³H]D-serine for 60 min, washed, and then incubated in Ringer containing 1mM indicated unlabeled amino acid. Extracellular radioactivity counted at indicate times is expressed as the mean fraction of total intracellular [³H]D-serine. Points represent mean ± SEM of 4 experiments with 5–6 oocytes per substrate tested. The amino acid L-glutamine is selectively transported by SLC1A5 over SLC1A4 and displayed similar selectivity for heteroexchange with D-serine.