A. Ishizuyaoka et S. Ueda, APOPTOSIS AND CELL-PROLIFERATION IN THE XENOPUS SMALL-INTESTINE DURING METAMORPHOSIS, Cell and tissue research, 286(3), 1996, pp. 467-476
In the amphibian small intestine, the epithelial transformation from t
he larval to adult type is mainly the result of degeneration of the la
rval epithelium and development of the new (adult) epithelium. In this
analysis at the cellular level, we chronologically examined apoptosis
and cell proliferation in the Xenopus intestine by using in situ nick
end-labeling of genomic DNA (TUNEL) and bromodeoxyuridine (BrdU) immu
nohistochemistry. During pre- and prometamorphosis, few apoptotic cell
s were detected by TUNEL, and a small number of proliferating cells ra
ndomly distributed in the larval epithelium were labeled by BrdU. At t
he beginning of the metamorphic climax, when primordia of the adult ep
ithelium were first detected, numbers of apoptotic cells suddenly incr
eased in the larval epithelium, whereas numbers of proliferating cells
increased only in the adult epithelium. Subsequently, a dramatic cell
loss of the larval epithelium and a rapid growth of the adult epithel
ium occurred. Following complete epithelial replacement, the adult epi
thelium became differentiated into a simple columnar epithelium posses
sing a cell renewal system similar to that of mammalian intestinal epi
thelium. These results indicate that larval epithelial apoptosis progr
esses simultaneously with active proliferation of the adult epithelium
during the early period of metamorphic climax, which coincides with t
he modification of the basement membrane lining both types of epitheli
a.