The ontogenesis, postnatal development and ageing of the endocrine
pancreas in mammals have not been
extensively studied. In order to improve understanding of this organ,
we studied the buffalo pancreas during
fetal and postnatal development. Glucagon, insulin and somatostatin
immunoreactive cells (i.c.) were first
seen in 2-mo-old embryos. Pancreatic polypeptide (PP) i.c. were
observed during the 3rd month of gestation.
The early embryo pancreas was almost totally composed of endocrine
tissue. The endocrine portion only
slightly increased in mass with animal growth, whereas the exocrine
portion noticeably increased in mass
during the late fetal and postnatal periods. In adults, therefore,
the exocrine portion was more evident than
the endocrine portion. Three types of islet were observed in fetal
and young buffalos: small, large and PP-islets. The small
islets were composed of insulin, glucagon,
somatostatin and PP i.c. The large islets were
primarily composed of insulin i.c. and a few glucagon, somatostatin
and PP i.c. The PP islets were mostly
composed of PP i.c. with a few somatostatin, insulin and glucagon i.c.
The number of large islets greatly
diminished by adulthood. Glucagon, insulin, somatostatin and PP i.c.
were also seen scattered in the
exocrine parenchyma and along the duct epithelium. In the duct
epithelium, these cells were either single or
grouped, and they sometimes formed a protrusion projecting towards
the connective tissue. These
morphological features were primarily observed in fetuses and young buffalos.