Alleviation of carbon tetrachloride-induced chronic liver injury and related dysfunction by L-tryptophan in rats.

We examined whether L-tryptophan (Trp) alleviates carbon tetrachloride (CCl4)-induced chronic liver injury and related dysfunction. Fifty rats were classified into four groups: the first (15 rats) served as the control; the second (10 rats) received subcutaneous injections of CCl4 (1.0 mL/kg) twice weekly for 8 weeks; the third (15 rats) received daily intraperitoneal injections of Trp (50 mg/kg) for 2 weeks after 6 weeks of CCl4 treatment; the fourth (10 rats) received both treatments. The activities of serum transaminases and the content of liver total hydroxyproline increased after 6 and 8 weeks of CCl4 treatment. The concentrations of serum albumin and liver protein and the in vitro activity of liver protein synthesis fell after 8 weeks of the treatment. Trp administration alleviated all these changes. At 6 and 8 weeks of CCl4 treatment the serum triglyceride concentration fell, whereas the liver triglyceride and lipid peroxide concentrations were elevated. Trp administration hardly affected these changes. These results indicate that Trp alleviates CCl4-induced chronic liver injury possibly by maintaining the activity of protein synthesis.