Influence of diethyl maleate and cysteine on tissue glutathione and growth in broiler chickens.

The objectives of this study were to determine the effects of diethyl maleate (DEM) and l-cysteine (L-Cys) on tissue glutathione (GSH) and growth in male broiler chickens. In Experiment 1, broilers were treated with DEM (0, 1.5, 3, 6, or 12.0 mmol/kg BW, i.p.). After 1 h, maximum GSH depletions were to 9, 24, 20, 19, and 35% of control (0 mmol DEM/kg) for liver, lung, kidney, heart, and brain, respectively. In Experiment 2, time-course changes following 1.5 mmol DEM/kg (i.p.) were determined; time-controls received an equal amount of corn oil (CO, .25 mL/kg BW). Levels of GSH in all tissues were low at 1 and 2 h after DEM in comparison to time-control values. Tissue GSH concentrations returned to values that were not different from controls by 5 h in liver and kidney, by 12 h in heart, and by 24 h in brain and lung. In Experiment 3, the effects of feeding a control diet (0% L-Cys) or one supplemented with 1% L-Cys from 3 to 7 wk of age with weekly i.p. injections (at 3,4,5, and 6 wk of age) of DEM (1.5 mmol/kg BW) or CO (.25 mL/kg BW) on growth rate and tissue GSH were determined. There were no differences in BW among treatment groups between 3 and 6 wk of age. Although there were no differences in 7-wk BW between controls (0% L-Cys/CO) and birds treated with DEM fed either diet, the 1% L-Cys/CO group was heavier (P < .05) than either the 0% or 1% L-Cys/DEM groups, and heavier (P = .066) than controls at 7 wk of age. At 5 wk of age, 1% L-Cys raised GSH concentrations in liver, kidney, lung, and duodenum, but had no effect on heart GSH in birds treated with either CO or DEM. Control hepatic GSH concentrations were higher at 7 than at 5 wk of age. With the exception of duodenal GSH in CO birds, 1% L-Cys had no effect on tissue GSH concentrations in 7-wk-old birds. The results of this study provide an initial characterization of GSH metabolism in commercial male broilers and indicate that DEM produced dose- and time-dependent changes in GSH similar to reported changes in mammals. Results of this study also indicate that increased tissue GSH may be beneficial for growth.