The time-course of changes in mucosal architecture and epithelial cell production and cell shedding in the small intestine of the rat fed after fasting.

Rats were starved for 3 days, then either allowed access to food or continued in starvation. The following measurements on the upper jejunum were made on groups of refed and starved rats at nine time intervals after refeeding: villus height, crypt depth, crypt/villus ration, rate of cell production per crypt, and number of epithelial cells shed per villus in 5 minutes. Villus height increased 2 hours after refeeding, while crypt depth changed less dramatically. Crypt/villus ratio was unchanged. The number of shed epithelial cells per villus was reduced below the starved level for 4 hours after refeeding, and did not rise significantly above the starved level until 9 hours; the rate of cell production was not significantly increased until 12 hours after refeeding. No evidence for a reserve of cells in G2 was found, and the 3 hour lag between the rise in cell shedding and the increase in cell production would probably not give enough time for cells in G1 to pass through S and G2. It is concluded that these observations do not support the hypothesis that increased cell shedding from the top of the villus stimulates increased cell production in the crypts of Lieberkuhn.