Sodium retention by rats bearing the Walker carcinosarcoma 256

¹ Laboratory of Physiology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland

Sprague-Dawley rats bearing the Walker tumor and remaining in nitrogen balance, during the later stages of tumor growth invariably excreted less than normal amounts of their Na and Cl intake. Potassium excretion during tumor growth remained essentially unaltered. Sodium retention occurred when the tumor was 10% or more of the body weight. Extirpation of the tumor from a rat during a period of Na retention resulted in a prompt return of the Na and Cl excretions to normal. Tumor-bearing rats that have retained Na for prolonged periods have hypertrophied adrenals with enlarged sinusoids; and such rats ingesting a basal diet containing 20% casein also show zona glomerulosa enlargement. Balance studies showed that the amount of Na found in the tumor accounted for almost all of the total Na retained during the study. Changes in concentration of Na, Cl, K, N and water in the carcasses of tumor-bearing rats were similar to concentration changes reported for undernourished rats (Na, Cl and N increased, K and water decreased).