The effect of protease treatment on the uptake of L-[³H]-glutamate into arsenite-treated erythrocytes. (A) Uninfected human erythrocytes were incubated with 0.5 mg/mL trypsin or chymotrypsin for 30 minutes at 37°C either before (white bars) or after (gray bars) treatment with sodium arsenite. Cells treated with arsenite, but not with either protease, served as the control (black bars). After the treatments, the uptake of L-[³H]-glutamate was measured for 10 minutes at 37°C. L-[³H]-glutamate uptake is expressed in terms of a distribution ratio. (B) Erythrocytes were treated with sodium arsenite and an aliquot of the treated cells was taken for the purpose of measuring the uptake of L-[³H]-glutamate. The arsenite-treated cells cells were then treated with 0.5 mg/mL chymotrypsin for 30 minutes at 37°C and a second aliquot was taken for determining the uptake of L-[³H]-glutamate. The cells were then treated for a second time with arsenite, and an aliquot taken for the purpose of determining L-[³H]-glutamate uptake. They were then treated again with 0.5 mg/mL chymotrypsin and a further aliquot was taken for the determination of L-[³H]-glutamate uptake. A third and final treatment of the cells with arsenite was followed again by a determination of L-[³H]-glutamate uptake. All uptake measurements were made for 10 minutes at 37°C. L-[³H]-glutamate uptake is expressed in terms of a distribution ratio. All data were averaged from 3 independent experiments and are shown ± SEM.