The role of apoptosis in atrophy of the small gut mucosa produced by repeated administration of cytosine arabinoside.

Progressive atrophy of ileal crypts and villi following daily administration of cytosine arabinoside to mice was found to be the result of suppression of mitosis and marked enhancement of apoptosis in the crypt epithelium. The amount of apoptosis produced by each dose decreased as the atrophy advanced. Mucosal regeneration after cessation of administration of the drug was due to increased mitosis in the crypts, and was associated with complete restoration of susceptibility of the crypt cells to further doses. During early regeneration, the wave of increased mitosis was accompanied by a wave of mildly increased apoptosis.