This study was conducted to investigate the role of tumor necrosis factor-alpha (TNF-alpha) and interleukin-2 (IL-2) in inducing cancer cachexia, and the results were compared with those obtained from our previous study on Fisher 344 rats with methylcholanthrene-induced sarcoma. Three groups of male Fisher 344 rats received one of the following regimens: 4 x 10(4) IU of human recombinant TNF-alpha per rat per day subcutaneously (sc) for 5 consecutive days (n = 5), 3.5 x 10(5) U human recombinant IL-2 per rat per day sc for 14 consecutive days (n = 5), or normal saline (n = 5). The activities of both phosphoenolpyruvate carboxykinase (PEPCK) and malic enzyme (ME) were increased slightly in the IL-2 group. Furthermore, LPL activity was significantly increased in the adipose tissue of the TNF group and in the cardiac muscle of the IL-2 group, but not in that of the TNF group. These results show that there is a significant difference between the metabolic alterations seen in the tumor-bearing state and those induced by either TNF-alpha or IL-2 alone. Thus, it is unlikely that IL-2 or TNF-alpha is the sole mediator of cancer cachexia in this tumor and rat model.