Taurine uptake by chick embryo retinal neurons and glial cells in purified culture

Abstract

The properties and cellular distribution of a high‐affinity uptake mechanism for taurine have been investigated using separate populations of purified chick embryo neural retina neurons and glia. Purified neuronal monolayers, cultured in serumfree medium, were incubated in radioactive taurine under different conditions and studied autoradiographically and biochemically. Labeling with radioactive taurine was detected in the perikaryon of most of the neurons present in the cultures. Neuronal uptake occurred by means of a high‐affinity mechanism which was completely inhibited at low temperatures or in the absence of sodium ions. The uptake was linear for at least 1 hr and, as is the case in vivo, could be inhibited by γ‐aminobutyric acid (GABA) or β‐alanine. Incubation in ouabain, glutamate, or high K⁺ concentrations failed to cause any increase in the amount of taurine released by neurons preloaded with the radioactive amino acid. The rather widespread distribution of high‐affinity taurine uptake was confirmed using separate retinal cultures rich in glial cells. Practically 100% of the glial cells appeared labeled after incubation in 10⁻⁷ M [³H] taurine, and this uptake was also inhibited by low‐temperature, Na⁺‐free medium, GABA, or β‐alanine. Several pieces of evidence indicate that high‐affinity taurine uptake coexists with uptake mechanisms for other amino acids, such as GABA, glutamate, and aspartate, in retinal neurons as well as glial cells. These in vitro populations offer a promising experimental system for the investigation of the effects of taurine on retinal cells.