Stress ulcers in rats: the role of food intake, body weight, and time of day.

Rats were housed in activity wheels (n = 32) or in hanging cages (n = 32) for 2 weeks. Food intake of rats in hanging cages was curtailed to match body weight to that of the activity group. All rats then received 6 g of food at one of four different times of day (n = 8, each mealtime) for 4 consecutive days and were sacrificed 24 h after the last meal. Twenty-three rats in the activity group and 13 rats in the hanging cage group had ulcers in the glandular portion of the stomach. Ulcers were significantly larger and more numerous in the activity group, and activity levels were highly correlated with area of ulceration. In both groups, terminal body weight was also significantly correlated with area of ulceration. No statistically reliable mealtime effects were observed because of large within-group variability. Because many rats in hanging cages developed ulcers in the absence of wheel running, the results suggest that restricted food supply and loss of body weight are initiating factors in ulcer formation, while excessive wheel running contributes to the severity of ulcerations in the glandular stomach.