Abstract
The urine of rats maintained on exptl. diets and receiving dl-serine (100 mg. daily by stomach tube) was compared with that of rats receiving dl-alanine. In the serine groups, a significant proportion of the administered amino acid was excreted in the urine. In addition, in the first few days of serine adm., the urine contained protein and sugar, and the amts. of bisulfite-binding and of reducing substances were elevated. Ethanolamine probably occurred in later periods of the expt. These changes were not observed in the urine of animals receiving dl-alanine.