The toxic effects of long-term, oral administration of L-tryptophan in rats with portacaval shunt.

The oral, long-term administration of 200 mg/kg of L-tryptophan to rats previously submitted to a portacaval shunt causes significant loss of body weight, muscular hypertonicity and aggressivity, as well as marked alterations of the liver structure. Conversely, the same treatment is well tolerated by control animals. It is postulated that the derangement of tryptophan metabolism normally occurring in rats with portacaval shunt is by itself insufficient to induce behavioural changes and liver damage, which, on the contrary, develop when tryptophan metabolism is further altered by the administration of the amino acid to the animals for a long period of time.