AJP - Gastrointestinal and Liver Physiology, Vol 265, Issue 4 699-G703, Copyright © 1993 by American Physiological Society

ARTICLES

Origin of D-alanine present in urine of mutant mice lacking D-amino-acid oxidase activity

R. Konno, T. Oowada, A. Ozaki, T. Iida, A. Niwa, Y. Yasumura and T. Mizutani
Department of Microbiology, Dokkyo University School of Medicine, Tochigi, Japan.

Urine of mutant ddY/DAO- mice lacking D-amino-acid oxidase contained 13 times more D-alanine than that of normal ddY/DAO+ mice. Because D-alanine is a component of bacterial cell walls, the possibility that the urinary D-alanine came from intestinal bacteria was examined. In ddY/DAO- mice that were made germ free at birth and reared in a germ-free environment, the quantity of urinary D-alanine was found to be at a low level comparable to that of the normal mice. When these germ-free mice were made gnotobiotic by inoculation with gram-negative bacteria (Escherichia coli and Bacteroides vulgatus), the urinary D-alanine increased to a high level. When these gnotobiotic mice were further inoculated with gram-positive bacteria (Bifidobacterium longum and Eubacterium aerofaciens), the urinary D-alanine increased further. These results indicate that most of the urinary D-alanine of the conventionally reared ddY/DAO- mice is of gastrointestinal bacterial origin.

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