The activity of enzymes involved in glutathione redox cycle and the level of glutathione in the liver. The activity of GP (a), GR (b) and the level of total glutathione (c), GSH (d), GSH/GSSG (e). Enzyme activities and the level of glutathione were determined as described in Materials and methods. Results are mean ± SEM. Time course of control and proline groups are denoted by solid line and dotted line, respectively. A significant difference between the two groups is denoted by “asterisk” (*P < 0.05, **P < 0.01).