Histidine deficiency, food intake and growth in normal and Walker 256 carcinosarcoma-bearing rats

Male Sprague-Dawley rats with and without growing Walker 256 tumors were fed 3 isonitrogenous, isoenergetic, semisynthetic diets. The N sources of the 3 diets were casein, a complete free amino acid mixture simulating casein, and the same amino acid mixture but now totally lacking histidine. Tumor-free rats and host and tumor components of tumor-bearing rats showed identical growth on the casein and on the casein-simulating free amino acid diets. Change from complete amino acid diet to histidine-free diet depressed food intake identically in controls and tumor-bearers in early stages of tumor growth. In later stages of tumor growth, when tumor-induced hypophagia had become apparent on the complete diet, the histidine-free diet had a progressively less depressive effect on food intake in the tumor-bearers.