Pancreatic islets in Platyrrhini monkeys:Callithrix jacchus, Saimiri boliviensis, Aotus azarae, andCebus apella. A cytological and immunocytochemical study

A histochemical and immunocytochemical study was performed to describe the cellular localization of four hormones in pancreatic tissue of the Callithricidae and Cebidae families belonging to Platyrrhini monkeys. Insulin, somatostatin, glucagon, and gastrin immunoreactive cells were detected in the pancreatic islets at light microscope level. Beta cells (insulin positve) were distributed in a peripheral mantle or in irregular clusters in a polar region of the islet. Also little groups (small islets) from three to six beta cells distributed in the pancreatic stroma were observed in all the species. A constant feature was the presence of neuroinsular complexes. The alpha cell population was composed of orangeophiles or phloxinophile cells and presented an heterogeneous composition as the result of their granular type (difference in immunocytochemical affinity). Alpha 1 cells (somatostatin) were scattered between the other cells or in the periphery of the islets, while alpha 2 cells (glucagon) were distributed in three different ways: (1) occupying polar positions; (2) disseminated in small groups; or (3) arranged in cord-like disposition. One or two G cells (gastrin) were found in few islets.