The Avian Pancreatic Islets: A Comparison Across Species

Abstract

The mammalian pancreas has a remarkable ability to maintain glucose homeostasis, through the production of the blood glucose lowering hormone insulin, and its counter‐regulatory hormone glucagon. The concept of avian diabetes arose in early studies of Minkowski in the late 1800's, which demonstrated that removal of the pancreas in domestic fowl and geese did not result in the development of diabetes. A species that deviates from this is horned owls which develop hyperglycemia and die following pancreas removal. Prior studies have demonstrated that the chicken pancreas contains more glucagon‐producing alpha cells compared to insulin‐producing beta cells. This is reflected in low blood levels of insulin in chickens. We hypothesize that species differences may exist in the expression patterns of pancreatic islet cells in birds allowing some to persist after pancreatectomy, whereas other birds perish as a result of hyperglycemia. In the present study, we employed immunohistochemistry to compare the density of alpha and beta cells in pancreatic tissue across the avian species. Studies were conducted on Mourning dove, Hooded Siskin, Collared Warbling Finch, and House Wren and we found that alpha cells were denser in the avian pancreas relative to beta cells. The study has been extended into other species such as Cinereous Conebill, Rufous Collared Sparrow, Amazilia Hummingbird, and Mountain Parakeet.