Sodium-dependent high-affinity uptake of taurine in cultured cerebellar granule cells and astrocytes.

Taurine uptake in cultured cerebellar granule cells and astrocytes consisted of a saturable high-affinity component and nonsaturable diffusion. The transport constant (Km) was significantly lower and the maximal velocity (V) higher in granule cells than in astrocytes. The uptakes were strictly sodium dependent and also moderately decreased in potassium-free medium. The specificity profile of taurine uptake was similar in both cell types, hypotaurine, beta-alanine, and guanidinoethanesulphonic acid being the most potent inhibitors, followed by GABA and homotaurine. Glutamate inhibited taurine uptake more in astrocytes than in granule cells. In principle, the uptake systems were similar in granule cells and astrocytes, exhibiting features characteristic of uptake of a neurotransmitter or -modulator.