The rat retinal pigment epithelium accumulated glutamate and taurine by saturable, temperature and Na(+)-dependent mechanisms. 2. Glutamate and taurine showed high and low affinity transport systems, with a Km of 30 microM and 80 microM, respectively. 3. The transport rates of both amino acids decreased during maturation of retinal pigment epithelial cells while their kinetic characteristics were not modified. 4. The results suggest an involvement of the retinal pigment epithelium in the regulation of glutamate and taurine levels in the neural retina and support its role as part of the blood retinal barrier.
