Protein depletion and energy retention in rats with ventromedial hypothalamic lesions

The catabolic effect of bilateral lesions in the ventromedial are of the hypothalamus (VMH) was studied in nitrogen-balance experiments and compared with the effect of a sham-operation in control animals. A transitory (24 h) increase in urine nitrogen was found in the controls, while in the lesioned animals, a persistent increase was found as long as the animals were fed. Fasting (48 h) eliminated the difference in urea excretion between the groups. Food-dependent effects of the VMH lesion are suggested. The changes in body and organ composition of VMH-lesioned animals, kept for 4 months on a food intake close to normal, were studied. The massive increase of body lipids and marked decrease of body protein and water was primarily due to increased subcutaneous-and abdominal-fat, and reduced skeletal and skin protein. An almost normal composition of the liver and close to normal amounts of protein in the viscera demonstrate that at least some tissues in VMH animals are able to maintain a normal protein content. Hyperphagia as a means to counteract the increased amino acid catabolism and to sustain the lean body mass is discussed.