Effects of Low Protein Diets or Feed Restriction on Rat Lung Glutathione and Oxygen Toxicity

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Abstract
Male rats weighing 200–250 g were fed a 25% casein diet in restricted amounts or ad libitum or one of two low protein diets (3 and 0% casein) ad libitum. Decreased tolerance to hyperoxic stress was observed only in the rats fed low protein diets. These animals had a median death time of 49–50 h compared to 58–69 h for feed-restricted or normal control groups. Death was due to accelerated development of lung edema. Changes in total lung levels of glutathione reductase, glucose-6-phosphate dehydrogenase or catalase did not correlate with oxygen sensitivity. Lung glutathione levels were related to the amount of sulfur-containing amino acids in the diet and were depressed in the feed-restricted as well as the protein-restricted groups. However, feed restriction alone did not enhance oxygen toxicity. We conclude that a decrease in lung glutathione may be partially responsible for the increased oxygen sensitivity in the protein-deficient rats, but that other factors are necessary for explanation of the relative oxygen tolerance of the feed-restricted animals with reduced levels of glutathione in the lung.