Inhibitory effect of triethyltin on taurine transport by glioma cells

The effects of triethyltin (TET) on the transport of taurine, glutamate, lysine, Na+, K+ (using 86Rb+ as tracer), and Cl- by LRM55 glioma cells were examined. Taurine transport was inhibited by TET at much lower concentrations (IC50 = 2.5 microM) than either glutamate or lysine transport (135 and 110 microM, respectively). TET had no significant effect on Na+, Cl-, or 86Rb+ influx at the low concentrations greater than 100 microM. The failure of low concentrations (less than or equal to 10 microM) of TET to affect ion transport indicated that inhibition of taurine transport was not secondary to effects of TET on ion movements or gradients. This conclusion was supported by the observation that neither ouabain nor furosemide, which do affect ion movement and gradients, strongly inhibited taurine transport. Uncouplers and inhibitors of oxidative phosphorylation (cyanide, 2,4-dinitrophenol, and carbonyl cyanide-m-chlorophenyl hydrazone) also had only small effects on taurine transport, suggesting that inhibition by TET was not secondary to possible effects on oxidative phosphorylation. TET had no effect on the efflux of taurine from LRM55 cells at the low concentrations that inhibit uptake, but it induced a nonspecific increase in membrane permeability at much higher concentrations (greater than 100 microM). Tri-n-propyltin and tri-n-butyltin were also potent inhibitors of taurine transport (IC50 = 2.3 and 11 microM, respectively), but trimethyltin was much less potent (144 microM).