An immunohistochemical study of the endocrine pancreas of the African ice rat, Otomys sloggetti robertsi.

The African ice rat, Otomys sloggetti robertsi, is a member of the subfamily Otomyinae, in the superfamily of Muroidea, to which all rodents belong. Very little is known about this unique family of rodents. The study reported here examines the endocrine pancreas of this species using immunohistochemical techniques. The islets of Langerhans were scattered in the exocrine pancreas and tended to be quite small. Scattered single endocrine cells (mostly immunoreactive for insulin) were found in the exocrine pancreas and were not generally associated with ducts (as marked by pan-cytokeratin labeling). The normal islet architecture of insulin in the center and glucagon, somatostatin (SS) and pancreatic polypeptide (PP) in the rim was observed, but the islets tended to have 2-3 layers of glucagon immunoreactive cells. Examining for rarer endocrine cell types, we found that cocaine amphetamine regulated transcript (CART) immunoreactive cells were co-localized with SS; and peptide YY (PYY) immunoreactive cells could be found that were singly immunoreactive or co-localized with either PP or glucagon. Ghrelin cells were not found. MafA co-localized only with the insulin cells, while MafB, which localizes to the glucagon cells, also showed a low level of immunoreactivity in most insulin immunoreactive cells. The Nkx family of transcription factors (Nkx6.1 and 2.2) and PDX-1 were all detected in the pancreas in a similar manner to that seen in mouse and rat. In conclusion, the endocrine pancreas of the African ice rat is quite similar to that of other studied rodents, but these animals have more glucagon and SS cells than rat (Rattus) or mouse (Mus) species.