Ultrastructural characterisation of periinsular pancreatic acinar cells in the hibernating dormouse Muscardinus avellanarius

In a previous study we analysed the exocrine pancreas of the hazel dormouse Muscardinus avellanarius, demonstrating several structural modifications of teleinsular acinar cells (located at a distance from the Langerhans islets) during the hibernating cycle. In the present study, we investigated the periinsular acinar cells (closely surrounding the Langerhans islets) of the same dormouse. by combining morphological, morphometrical, and immunocytochemical analyses. Our observations demonstrate that, during hibernation, several cytoplasmic organelles undergo structural modifications: cells, nuclei and zymogen granules decrease in size. and alpha -amylase content falls: however, upon arousal, ail euthermic features are restored. All these data are consistent with a marked reduction in metabolic activities (especially protein synthesis and secretion) during hibernation, and their resumption upon arousal. Moreover, when changes of periinsular cells are compared with those of teleinsular cells, it is evident that periinsular cell structural constituents are more affected by the functional rest during hibernation. This is probably related to the paracrine action of the islet hormones on the surrounding acinar cells.