Two Types of Islet α Cells in Different Parts of the Pancreas of the Dog

Abstract

A CRITICAL evaluation of the argyrophil reaction in the islets of Langerhans in different vertebrates revealed that only a certain number of the α cells are argyrophil (= α₁ cells), while the rest (= α₂ cells), like all the β cells, lack this property^1–7. Differences were demonstrated between the two types of α cells also with regard to their localization within the islets, the size and eccentricity of their nuclei and the metachromatic reaction with toluidine blue and azure A^4–7. The reports of Bencosme et al.^8,9 that the uncinate process of the dog pancreas is devoid of α cells and contains practically no extractable hyperglycæmic activity has lent strong support to the view that the α cells are a source of glucagon. The present investigation is an attempt to find which type of α cell is possibly associated with glucagon secretion by analysing how the α₁ and α₂ cells are regionally distributed within the pancreas of the dog.