Differential proliferation of somatostatin and glucagon cells in rat pancreatic islets submitted to various stimuli

Abstract

The populations of endocrine cells in pancreatic islets are subjected to striking fluctuations in their size when subjected to sustained stimulation and/or inhibition of their secretory activity. The stimulation of a specific endocrine secretion is followed by proliferation of its producing cell, a situation that is reversed after interruption or inhibition of the stimulus. Morphometric and cytological modifications of somatostatin and glucagon producing cells (D and A cells respectively) in the islets of Langerhans have been studied by electron microscopy, immunocytochemistry and morphometry in pancreas of rats submitted to the following experimental conditions: 1) Adrenalectomized (ADX), 2) ADX treated with hydrocortisone, 3) Diabetic and 4) Cysteamine (CSH) treated rats. In addition to ultrastructural changes, the populations of A and D cells were analyzed morphometrically applying a computerized system for light microscopy of paraffin sections immunostained with peroxidase-antiperoxidase (PAP) technique. Glucagon cell population displayed striking alterations in fine structural features and in the volume density in the different experimental conditions examined. By contrast, the cytological organization and the size of somatostatin cell population were little or not affected except in the diabetic rats where the massive degeneration of beta cells grossly distorted the structure of the islets. These observations led to the conclusion that the population of D cells constitutes a stable of endocrine system, at variance to the profound modifications occurring in A cells when they are submitted to various experimental conditions that stimulate or inhibit their secretory activity.