Taurine uptake by glial cells in the bullfrog sympathetic ganglia

Taurine uptake was studied in the bullfrog sympathetic ganglia. High- and low-affinity components were detected after subtraction of nonsaturable influx from total uptake in a concentration range from 34 nM to 8mM. Taurine uptake was strictly sodium dependent and the sodium dependency curve was sigmoidal, with a Hill number of 1.6, indicating that at least two sodium ions are required for the transport of one taurine molecule. External sodium ion affected both K(m) and V(max) for taurine uptake. Taurine uptake was inhibited by ouabain, but not by tetrodotoxin. These results suggest that sodium concentration gradient across plasma membrane may be the main driving force for taurine uptake. Electron and light microscopic autoradiography showed that glial cells were heavily labeled by [(3)H]taurine while ganglion cells were slightly labeled. The present data suggest that glial uptake may contribute to terminating the effect of taurine in the bullfrog sympathetic ganglia.