Tumor-induced alterations in brain neurotransmitter and plasma ammonia concentrations are normalized twenty-four hours after tumor resection.

Tumor-induced anorexia was accompanied by significant elevations in plasma ammonia and lactate and by alteration of the plasma amino acid profile. The brains of anorectic tumor-bearing rats had increased levels of glutamine and most large neutral amino acids. Dopamine and serotonin metabolism were also increased in several brain regions of these rats. Resection of the tumor resulted in the normalization of most of these aberrations in blood and brain within 24 hrs. These results demonstrate a rapid reversal of tumor-induced biochemical alterations shortly after tumor removal and suggest that these aberrations may be secondary to hyperammonemia.