Dietary regulation of adenosine deaminase activity in stomach, small intestine and spleen of mice.

Activity of adenosine deaminase (ADA) and its regulation by dietary restriction were studied in the stomach, small intestine and spleen of mice. ADA activity (U/mg protein) was highest in the stomach, followed by small intestine and spleen of mice on normal diet. The activity decreased significantly in the stomach (41%) and small intestine (45%) of 24 hr fasted mice, when compared to mice fed ad-libitum. However, ADA activity in spleen did not show any change by dietary intervention. Refeeding of fasted mice for 24 hr restored the activity of ADA in tissues. In addition, dietary restriction (alternate days of feeding for three months) had a cumulative effect, whereby ADA activity decreased significantly in the stomach (53% on the day of feeding and 60% on the day of fasting) and small intestine (50% and 54% on the day of feeding and fasting, respectively) without any change in activity in spleen. These findings indicate that dietary restriction reduces ADA activity in a tissue-specific manner. Long-term dietary restriction leads to a cumulative adaptation in lowering the ADA activity of GIT, but not in spleen.