Distribution of endocrine cells displaying immunoreactivity for one or more peptides in the pancreas of the adult vervet monkey (Cercopithecus aethiops).

Abstract

Our previous studies on the Chacma baboon revealed that the most striking difference between islets of the ventral and dorsal regions of the pancreas was their content of A and pancreatic polypeptide (PP) cells with A cells predominating in the tail and PP cells in the uncinate and head. Cells displaying dual immunoreactivity for both glucagon and PP were also observed. The objective of this study was to establish baseline parameters of the adult Vervet monkey (Cercopithecus aethiops) pancreas so that it could be used as a primate model to investigate possible therapies for diabetes. Vervet-monkey pancreas was divided into uncinate, head, and tail regions, and the tissue processed for immunolabelling for pancreatic peptides using avidin-biotin-peroxidase as marker. Dot-blotting and absorption controls for antibody specificity were included because of the shared amino acid sequences in pancreatic polypeptide (PP), neuropeptide Y (NPY), and peptide YY (PYY). Endocrine cell distributions and the percentages of each cell type per region were calculated for each monkey. A significant difference in the percentages of PP cells (P = 0.02) was observed between uncinate and tail regions, the distribution of NPY cells was similar to that of the PP cells, and all other distributions were similar to those reported in the literature for most animals studied. Cells displaying dual immunoreactivity for glucagon and PP or NPY, PYY and NPY, or PP, PP and somatostatin and glucagon and insulin were identified and mapped throughout the pancreas. Most co-localizations occurred in the uncinate region. Co-localization of glucagon and insulin has not, to our knowledge, been reported previously in the adult pancreas. Pancreatic endocrine cell distribution in the adult Vervet monkey was found to be very similar to most other animals studied. The occurrence of cells displaying dual immunoreactivity for a number of different combinations of pancreatic peptides suggests an interesting plasticity of endocrine cells even in the adult animal.