The current study characterizes a mediated transport for GSH uptake in murine fibroblasts NIH3T3. The presence of GSH mediated transport is indicated by the behaviour of GSH uptake time-course, as well as by kinetic saturation and the specific inhibition of the initial rate of GSH transport. Moreover, a concentrative GSH uptake has been measured, whose driving force may be due to a change of membrane potential and the direct involvement of ATP. Hyperbolic kinetic saturation shows a single mediated transport with high affinity for GSH (Km = 0.209 +/- 0.03 mM). High specificity of this GSH transporter for the entire structure of GSH is also demonstrated. To summarize, GSH uptake into NIH3T3 cells occurs by an active transport system and shows characteristics similar to ATP-dependent mechanisms previously identified in hepatocyte membranes. Moreover, a possible physiological role of this GSH transporter related to NIH3T3 cell proliferation has been hypothesized.