Endogenous formation of 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3- carboxylic acid in man as the possible causative substance of eosinophilia-myalgia syndrome associated with ingestion of L-tryptophan.

1-Methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCA) is now thought to be a possible causative substance of eosinophilia-myalgia syndrome associated with ingestion of L-tryptophan. In the present study a factor affecting endogenous formation of MTCA in 32 healthy men is studied. Urinary excretions of MTCA and 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (TCCA) were measured by high-performance liquid chromatography (HPLC) with fluorometric detection after administration of a high or low protein diet as well as peroral tryptophan (0.5 g) or ethanol (0.4 g/kg). Blood ethanol and acetaldehyde levels were determined by gas chromatography after ethanol consumption. Both, the high protein diet and tryptophan resulted in a significant rise of urinary TCCA. In contrast, ethanol intake caused increased excretion of MTCA, though a relationship between blood acetaldehyde level and urinary excretion of MTCA was not shown. We showed for the first time that an elevation of urinary excretion of MTCA following ethanol consumption in man without ingestion of L-tryptophan tablets implicated eosinophilia-myalgia syndrome.