Feeding response of tumor-bearing rats to insulin and insulin withdrawal and the contribution of autonomous tumor drain to cachectic depletion

The Walker 256 carcinosarcoma growing in Sprague-Dawley rats and the Morris 5123 hepatoma growing in Buffalo rats both produce cachexia but have widely differing patterns of host metabolism and tumor growth. Both organisms respond to exogenous insulin with increased food intake and rate of weight gain of host. The insulin treatment response of food intake was 1.5 to 2 times and of body weight gain was 2 to 3 times that of tumor-free controls. Insulin does not accelerate tumor growth. On withdrawal of insulin, the reactive hypophagia seen in tumor-free rats does not occur in tumor bearers, and the host weight does not return to the expected untreated value as it does in tumor-free rats. Most of the weight gained during insulin treatment of tumor bearers above that gained by tumor-free rats is retained after withdrawal of insulin. A computer model based on the inference from these results, that the tumor-bearing host is blind to body weight error, indicates that this abnormality of feeding control could account for only about one-third of the observed depression of host weight and food intake.