[Effect of L-tryptophan, nicotinamide, L-methionine and 1-methylnicotinamide on the embryotoxic effect of various substances].

There are several reports in the literature indicating that embryotoxic substances influence the nicotinamide adenine dinucleotide (NAD) metabolism. Therefore, the effect of different metabolites of the NAD metabolism--i.e. nicotinamide, L-tryptophan, 1-methylnicotinamide as well as L-methionine - upon the embryotoxicity of 6-aminonicotinamide, hydroxy-urea, 6-mercaptopurine, and cyclophosphamide was studied. 1. The embryotoxicity of 6-aminonicotinamide is completely prevented by nicotinamide and L-tryptophan, but enhanced by L-methionine and 1-methylnicotinamide. 2. Hydroxy-urea produced a resorption rate of 30% of the fetuses under the conditions applied. In the presence of L-methionine, the rate is lower; the other substances do not show any effect. 3. All substances used enhance the embryotoxicity of 6-mercaptopurine. There are, however, marked differences between them. 4. The embryotoxicity of cyclophosphamide is especially enhanced by a combined administration of nicotinamide + L-methionine. L-Tryptophan, on the other hand, increases the weight of the embryos.