Intestinal microflora and aging: age-related change of enzymes in the liver and the small intestine of germ-free and conventional rats.

The activities of various enzymes involved in detoxication and carbohydrate metabolism in the liver and the gastrointestinal tract of germfree (GF) and conventional (CV) rats, 8 and 40 weeks' old, were measured in relationship to intestinal microflora and aging. In 8-week-old rats, the activities of nitroreductase (NR) and aniline hydroxylase (AH) in the liver, and of alkaline phosphatase (ALP), maltase and lactase in the duodenum were higher in GF than in CV rats, but the activities of arginosuccinate synthetase (ASS) and lactate dehydrogenase (LDH) in the liver were higher in CV than in GF rats. In 40-week-old rats, the activities of NR and glucose-6-phosphatase dehydrogenase (G-6-PDH) of the liver and ALP, maltase and lactase of the duodenum were higher in GF than in CV rats, but those of ASS, UDP-glucuronyl transferase (UDP-GT), AH, beta-glucuronidase, and LDH of the liver were higher in CV than in GF rats. Compared between 8- and 40-week-old rats the activities of NR, beta-glucuronidase, LDH, and acid phosphatase increased with aging in both GF and CV rats. The specific activities of ASS in CV and UDP-GT and AH in GF rats decreased with aging. The total activities of ASS and AH in GF rats also decreased with aging. The activities of ALP, maltase and lactase decreased with aging in both GF and CV rats. Thus, these data suggested that there are influences of indigenous intestinal microflora and aging on the activities of various enzymes in the liver and gastrointestinal tract.