Mutagenicity of human urine caused by ingestion of fried ground beef

On ingestion of fried ground beef by humans, the urinary mutagenicity, as examined by the Ames test, increased rapidly and then decreased during a period of 12 hr to resume the original low level. The excreted mutagens were shown to differ from 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, the major mutagen in the cooked beef.