The effects of cyclooxygenase inhibitors on tumor-induced anorexia in rats

Interleukin-1 (IL-1) and tumor necrosis factor (TNF) are potent induces of prostaglandin (PG) synthesis and injection of PGE, IL-1, or TNF decreases food intake in healthy animals, whereas the anorexigenic effects of injected IL-1 and TNF are blocked by inhibitors of PG synthesis. It has been hypothesized that host secretion of IL-1 and TNF contribute to tumor-induced anorexia. This study was undertaken to determine whether administration of PG inhibitors alters food intake in anorectic rats implanted with Walker 256 carcinoma.

Groups of six tumor-bearing rats were implanted with slow-release pellets containing ibuprofen, indomethacin, or acetylsalicylic acid. Food intake, tumor growth, and body temperature were monitored for 14 days and compared with control tumor-bearing animals implanted with placebo pellets.

Tumor growth was associated with anorexia, fever, weight loss, and increased leukocyte secretion of IL-1 and TNF. Indomethacin and ibuprofen retarded tumor growth 30-40% and lowered body temperature compared with controls, but had no effect on food intake or body weight of tumor-bearing animals.

Prostaglandins do not mediate tumor-induced anorexia.