Glutathione transport in immortalized hle cells and expression of transport in HLE cell poly(A)⁺ RNA-injected Xenopus laevis oocytes

PURPOSE. To determine reduced glutathione (GSH) transport in cultured human lens epithelial cells (HLE-B3) and plasma membrane vesicles and to study the expression of GSH transport in Xenopus laevis oocytes injected with poly(A)⁺ RNA from HLE-B3 cells. METHODS. Confluent HLE-B3 cells pretreated with 10 mM DL-buthionine sulfoximine and 0.5 mM acivicin were used in GSH uptake studies. The uptake of ³⁵S-GSH was performed for 30 minutes in either NaCl medium (Na⁺-containing) or choline chloride medium (Na⁺-free) at 37°C and 4°C. The molecular form of ³⁵S uptake was determined by high- performance liquid chromatography. GSH uptake kinetics were studied in acivicin and buthionine sulfoximine-treated HLE-B3 cells in NaCl medium in the concentration range 0.01 μM. The transport of GSH and the effect of Na⁺ on uptake also were determined in mixed plasma membrane vesicles from HLE-B3 cells. In oocyte expression studies, HLE-B3 poly(A)⁺ RNA was injected into X. laevis oocytes and GSH uptake experiments were performed 3 days after injection. The uptake of ³⁵S-GSH and GSH efflux rates were determined in HLE-B3 poly(A)⁺ RNA-injected oocytes. RESULTS. No significant difference was found in the uptake of 1 mM GSH ± acivicin (17.7 ± 4.3 versus 15.7 ± 1.4 picomoles/min^-+ per 10⁶ cells). However, GSH uptake was significantly lower in Na⁺ -free medium compared with Na⁺-containing medium (10.3 ± 0.7 versus 16.8 ± 0.9 picomoles/min^-1 per 10⁶ cells; P < 0.01). GSH uptake in NaCl medium was carrier mediated. GSH uptake showed partial sodium dependency from 5 μM to 5 mM GSH in mixed plasma membrane vesicles from HLE-B3 cells. Oocytes injected with HLE-B3 poly(A)⁺ RNA expressed uptake and efflux of GSH. Uptake showed partial Na⁺ dependency at various GSH concentrations. The efflux rates were approximately 30-fold higher than those in water-injected oocytes (0.48 ± 0.03 versus 0.016 ± 0.005 (nanomoles per hour^-1 per oocyte, respectively). The molecular form of uptake in cultured cells and in oocyte studies was predominantly as intact GSH. CONCLUSIONS. HLE-B3 cells and plasma membrane vesicles transported GSH by a carrier-mediated process. HLE- B3 poly(A)⁺ RNA injected X. laevis oocytes expressed GSH transport. GSH uptake was partially Na⁺ dependent in all systems. HLE-B3 cells offer a useful model for characterizing GSH transport and for studying its regulatory role in the etiology of cataracts.