Effects of oxygen supply on protein metabolism in surgically injured rats. Oxygen as a nutrient.

The effect of various inspired oxygen concentrations on protein metabolism after surgery was investigated in rats. Surgical injury was produced by transecting the stomach. Rats were divided into three groups, i.e., a hyperoxic group, a hypoxic group, and a normoxic control group, which were supplied with 40%, 10%, and 21% oxygen, respectively, for 7 days after operation. All rats were fed intravenously (257 kcal/kg/day, kcal/N: 185.5) and whole-body protein turnover was measured using the constant infusion of 15N glycine technique developed by Picou and Taylor-Roberts. For six days after operation, the cumulative nitrogen balance was negative for the hypoxic rats, while hyperoxic rats showed a positive balance that was significantly higher than in control rats (p less than 0.01). Protein synthesis and breakdown rates increased markedly and the rate of synthesis exceeded that of breakdown in the hyperoxic group, but in the hypoxic group synthesis remained unchanged while breakdown increased moderately. These results indicate that oxygen, as a nutrient, is effective for improving postoperative protein metabolism.