DIFFERENTIAL PROLIFERATION OF SOMATOSTATIN AND GLUCAGON CELLS IN RAT PANCREATIC-ISLETS SUBMITTED TO VARIOUS STIMULI

The populations of endocrine cells in pancreatic islets are subjected to striking fluctuations in their size when subjected to sustained sti mulation and/or inhibition of their secretory activity. The stimulatio n of a specific endocrine secretion is followed by proliferation of it s producing cell, a situation that is reversed after interruption or i nhibition of the stimulus. Morphometric and cytological modifications of somatostatin and glucagon producing cells (D and A cells respective ly) in the islets of Langerhans have been studied by electron microsco py, 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 computeriz ed system for light microscopy of paraffin sections immunostained with peroxidase-antiperoxidase (PAP) technique. Glucagon cell population d isplayed striking alterations in fine structural features and in the v olume density in the different experimental conditions examined. By co ntrast, the cytological organization and the size of somatostatin cell population were little or not affected except in the diabetic rats wh ere the massive degeneration of beta cells grossly distorted the struc ture of the islets. These observations led to the conclusion that the population of D cells constitutes a stable of endocrine system, at var iance to the profound modifications occurring in A cells when they are submitted to various experimental conditions that stimulate or inhibi t their secretory activity.