ANTEROPOSTERIOR GRADIENT OF EPITHELIAL TRANSFORMATION DURING AMPHIBIAN INTESTINAL REMODELING - IMMUNOHISTOCHEMICAL DETECTION OF INTESTINAL FATTY-ACID-BINDING PROTEIN
A. Ishizuyaoka et al., ANTEROPOSTERIOR GRADIENT OF EPITHELIAL TRANSFORMATION DURING AMPHIBIAN INTESTINAL REMODELING - IMMUNOHISTOCHEMICAL DETECTION OF INTESTINAL FATTY-ACID-BINDING PROTEIN, Developmental biology, 192(1), 1997, pp. 149-161
To determine whether the remodeling of the well-organized intestinal e
pithelium during amphibian metamorphosis is regionally regulated along
the anteroposterior axis of the intestine, we raised a polyclonal ant
ibody against the Xenopus laevis intestinal fatty acid-binding protein
(IFABP), which is known to be specifically expressed in intestinal ab
sorptive cells, and examined immunohistochemically the differentiation
, proliferation, and apoptosis of the epithelial cells throughout X. l
aevis small intestine. During pre- and prometamorphosis, IFABP-immunor
eactive (ir) epithelial cells were localized only in the anterior half
of the larval intestine. At the beginning of metamorphic climax, apop
totic cells detected by nick end-labeling (TUNEL) suddenly increased i
n number in the entire larval epithelium, concurrently with the appear
ance of adult epithelial primordia. Subsequently, the adult primordia
in the anterior part of the intestine developed more rapidly by active
cell proliferation than those in the posterior part, and replaced the
larval epithelial cells earlier than those in the posterior part. IFA
BP-ir cells in the adult epithelium were first detectable at the tips
of newly formed folds in the proximal part of the intestine. Thereafte
r, IFABP expression gradually progressed both in the anteroposterior d
irection and in the crest-trough direction of the folds. These results
suggest that developmental processes of the adult epithelium in the X
. laevis intestine are regionally regulated along the anteroposterior
axis of the intestine, which is maintained throughout metamorphosis, a
nd along the trough-crest axis of the epithelial folds, which is newly
established during metamorphosis. Furthermore, the regional differenc
es in IFABP expression along the anteroposterior axis of the intestine
were reproduced in organ cultures in vitro. In addition, IFABP expres
sion was first down-regulated and then reactivated in vitro when the a
nterior part, but not the posterior part, of the larval intestine was
treated With thyroid hormone (TH) for extended periods. Therefore, it
seems that, in addition to TH, an endogenous factor(s) localized in th
e intestine itself with an anteroposterior gradient participates in th
e development of the adult epithelium during amphibian metamorphosis.
(C) 1997 Academic Press.