INSULIN REVERSES AMMONIA-INDUCED ANOREXIA AND EXPERIMENTAL CANCER ANOREXIA

Previous experiments suggest that experimental cancer-induced anorexia is associated with hyperammonemia and that daily injections of insuli n may attenuate the anorexia for several days. In the present study, w e determined whether similar daily insulin treatments would correct an orexia induced by the infusion of ammonium salts and compared this fee ding response with that of insulin-treated tumor-bearing (TB) rats. Da ily treatment of central and anorectic TB rats with systemically admin istered insulin for six days increased feeding in all control rats and 40% of the TB rats. AN insulin-treated groups exhibited equal degrees of hypoglycemia irrespective of anorexia. Basal concentrations of lac tate and glucagon were elevated in saline-treated TB rats. Plasma lact ate levels were normalized by insulin treatment, whereas glucagon war; normalized only in the TB rats that fed to insulin and increased furt her in TB rats that did not feed to insulin. Elevated hypothalamic tyr osine was reduced in insulin-treated TB rats that ate, and 5-hydroxy-i ndoleacetic acid was increased further when the rats did not eat. Insu lin also blocked anorexia resulting from the intravenous infusion of a mmonium salts. Hypothalamic concentrations of tyrosine and tryptophan were increased by the ammonia infusion and reduced significantly in in sulin-treated infused rats. These results indicate that insulin treatm ent can reverse experimental cancer-induced anorexia and hyperammonemi a-induced anorexia. Neurochemical changes associated with these treatm ents are also similar, but not identical.