Effects of Dietary DL-Methionine on Tissue Levels of Glutathione in Hypothyroid Chicks

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Abstract
Earlier studies have shown that dietary DL-methionine counteracts various effects associated with hyperthyroidism in chicks. A study has now been conducted to ascertain whether methionine counteracts, or augments, effects associated with hypothyroidism in chicks. The principal criteria were blood, liver, heart and muscle content of reduced glutathione (GSH). The hypothyroid state was induced by incorporating 6-propylthiouracil (PTU) into the diet. Its administration led to consistent increases in liver and breast muscle GSH, as did that of methionine. Combined supplementation led in nearly every case to still higher GSH levels. The data on heart, and particularly blood, are less clear-cut. On balance, though, they also support an interpretation of augmentation, rather than counteraction, of effects of methionine and PTU. Thus it has been shown that methionine synergizes, rather than antagonizes, the effects of hypothyroidism on tissue levels of GSH. This lends credence to the hypothesis of a specific antithyrotoxic effect of methionine.