ROLES OF SELENIUM AND SULFUR-CONTAINING AMINO-ACIDS IN PROTECTION AGAINST OXYGEN-TOXICITY

  • 1 January 1983
    • journal article
    • research article
    • Vol. 49  (2) , 148-153
Abstract
Tolerance and adaptation to hyperoxia are correlated with increases in antioxidant enzymes. This study evaluated whether Se deficiency would prevent an increase in glutathione peroxidase (GSHPX), a Se-containing enzyme, during O2 exposure, and, thus, inhibit adaptation. Because the Torula yeast-based diet, used to produce Se deficiency was also deficient in cysteine and methionine, the effects of these deficiencies were also evaluated. When rats were exposed to 80% O2 for 1 wk, mortality was 80% for rats deficient in both Se and the S-containing amino acids, 40% for Se-deficient rats, 35% for cysteine- and methionine-deficient rats and 0% for rats fed either a standard laboratory diet or a Se, cysteine- and methionine-supplemented Torula yeast diet. Only 1 of the 6 surviving rats with low Se and none of the rats from any other dietary group died during a subsequent 96 h of 98% O2, indicating adaptation to hyperoxia (LD50 for unadapted rats is 72 h). GSHPX activity (per g dry wt) was decreased 85% in lungs from unexposed rats fed the low Se diets. After O2 exposure, lung GSHPX activity was elevated in all dietary groups. Rats fed the high Se diets had a 47% increase in enzyme activity; rats with high Se had a 214% increase. Although hyperoxia caused a relatively high percentage increase in the low Se rats, the resulting absolute GSHPX activity was only 34-70% of that of unexposed high Se rats. Evidently, both Se and S-containing amino acids contribute to antioxidant defense. Although the stress of hyperoxic exposure produces an increase in glutathione peroxidase activity, the absolute lung GSHPX activity is better correlated with tolerance than with adaptation to hyperoxia.