Formation in vivo of deuterated methylthio metabolites of naphthalene from L-methionine (methyl-d--3).

Studies were carried out with deuterated methionine (methyl-d--3) to determine if methylthio metabolites of naphthalene were formed in vivo by reaction with methionine-derived metabolites. Rats were maintained on a methionine-free diet for nine days followed by eight days on the same diet supplemented with L-methionine-d--3 prior to administration of naphthalene. When naphthalene metabolites isolated from urine were characterized by GC and GC-MS procedures, it was found that the incorporation of deuterium into the methylthio metabolites, as well as into a catechol methyl ether, was approximately 40%. These results show that the methyl group was derived from methionine.