Fatty liver induced by injection of l-tryptophan

Abstract

l-Tryptophan caused the accumulation of neutral lipids in liver within 2.5 h after its intraperitoneal injection into rats. This accumulation of neutral lipids continued for about 24 h. Peripheral fatty liver was diagnosed histologically by Sudan III staining. The minimal effective dose was 0.5 mg/g of body weight. The level of cholesterol and phospholipids in liver did not alter. 3-Hydroxyanthranilic acid and l-kynurenine were as effective as l-tryptophan in inducing the accumulation of neutral lipids, but other metabolites of tryptophan, kynurenic acid, anthranilic acid, quinolinic acid, nicotinic acid and nicotinamide did not produce the lipid accumulation. The administration of other amino acids, such as l-leucine, l-lysine, l-tyrosine, l-threonine and l-methionine, did not increase the amount of total lipids in liver. Simultaneous administration of ATP, ADP, AMP, adenosine or folic acid with l-tryptophan prevented the fatty liver. A marked decrease in the concentration of ATP in the liver was shown by the administration of l-tryptophan or l-kynurenine. These observations support the concept that l-tryptophan-induced fatty liver is due to the decreased level of ATP. A possible mechanism of ATP depression by administered l-tryptophan is discussed.