The Effect of Methionine Supplementation upon the Tumor-Host Relationship in the Rat

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Abstract
Data are presented to demonstrate that the gain in weight of a transplanted sarcoma was independent of the gain in body weight of rats fed a 12% casein diet. Supplementation with methionine did not alter this independence but did increase the rate of gain of the body with respect to the tumor. Adding more nitrogen in the form of glycine or guanidoacetic acid together with the methionine increased this rate of gain of the body still further and evidence is presented to show that the rate of growth of the tumor was depressed in the larger animals fed the mixed supplements. The reduction in excretion of urea nitrogen in the presence of these various methionine supplements was demonstrated in normal rats fed a protein-free diet and in tumor-bearing rats fed the 12% casein diet. The catabolic activity, as measured by excretion of urea nitrogen, differed between protein-starved and tumor-bearing rats, the excretion decreasing to exceedingly low values in the protein-starved while it increased to high values as the tumor became large in the tumor-bearing rats. The mixed supplements of methionine and either guanidoacetic acid or glycine reduced the excretion of urea in the tumor-bearing animals when the loss of urea nitrogen was exceptionally high. The depleting effects of the tumor and of a protein-free diet were similar when measured in terms of electrophoretic patterns of plasma. The increase in plasma protein stores through methionine supplementation was also detected by these patterns.

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