Programmed cell death (apoptosis) is a normal characteristic of cells
with a limited life span like the enterocyte and the usual mode of dea
th for proliferative crypt cells subjected to radiation or chemotherap
y. The Bcl-2 proto-oncogene is considered a major regulator of apoptos
is. We investigated the relationship of enterocyte apoptosis and Bcl-2
expression in rat intestine and tissue culture cells. Fragmentation o
f DNA and levels of Bcl-2 transcripts were evaluated in rat enterocyte
fractions of the crypt-to-villus axis of differentiation and in IEC t
issue culture cells. A low percentage of isolated nuclei from each ent
erocyte fraction showed features of DNA fragmentation, including crypt
cells. Detectable DNA fragmentation was seen in IEC cells only when c
ells were subjected to long-term confluent culture conditions. Bcl-2 m
RNA was not detected in isolated rat intestinal cells but was detected
in IEC cells where its level increased with serum deprivation and lon
g-term culture. We conclude that increased Bcl-2 expression may be imp
ortant in rescue of proliferative enterocytes subjected to stress.