Influence of aging on gastric emptying of liquids, small intestine transit, and fecal output in rats.

The gastric emptying of a liquid meal, the small bowel transit, and the number of pellets and fecal output produced during a 24-h period, were studied in young (three months), adult (12 months) and old (24 months) male Wistar rats. The gastric emptying after 20 min of an intragastrically administered liquid meal containing phenol red and methylcellulose was significantly decreased in old rats. The small bowel transit after 15 and 30 min of the front of a charcoal and Arabic gum containing intragastrically administered meal was similar in the three age groups. The number of pellets and the mass of the feces produced during a 24-h period were significantly decreased with age, while the food intake was similar. The water content of the pellets was similar in the three age groups. These results show decreased gastric emptying of liquids and decreased stool mass in old rats, corresponding with the previously reported age-related changes in colonic smooth muscle contractility. Small intestinal transit was well maintained with age.