RESUMO
Objective:To investigate age-related histological and ultrastructural changes of the pancreas in Sprague-Dawley(SD)rats, and to provide a theoretical basis for the high incidence of pancreatic diseases in the elderly.Methods:Thirty 6-month-old specific pathogen-free male SD rats were fed until 6, 12, 18 and 25 months of age.Five rats of each age group were randomly selected, killed and then sampled to make histological(HE staining)and electron microscopic sections to observe age-related changes in pancreatic histology and ultrastructure.Results:The pancreatic tissue of rats showed increasing fibrosis with age, especially around the duct.Fat infiltration of the pancreatic tissue also increased with age( H=15.88, P=0.001). With the increase of age, the number(density)of pancreatic islets decreased gradually( F=3.55, P=0.039), but the average cross-sectional area of islets increased significantly( F=7.76, P=0.002), and the round and oval islets became irregular.Nuclear pyknosis, mitochondrial dehydration, mitochondrial swelling, and dilatation and loose organization of rough endoplasmic reticula were observed in the cytoplasm of pancreatic acinar cells and islet beat cells in aged rats.With the increase of age, the number of zymogen granules at the apical pole of pancreatic acinar cells of rats decreased( F=9.73, P<0.001), and the average area and total area of granules were significantly decreased( F=6.51, P=0.001; F=22.18, P<0.001); The number of non-senescent mitochondria and senescent mitochondria in the cytoplasm of acinar cells increased significantly( H=8.22, P=0.045; H=32.95, P<0.001); The amount of proinsulin in islet beta cells was significantly decreased( F=16.20, P<0.001). Conclusions:With aging, the rat pancreas exhibits a series of degenerative manifestations(stromal hyperplasia, adipose tissue infiltration, decreased numbers of zymogen granules in acinar cells, increases in the number of senescent mitochondria, reduced islets and reduced proinsulin in islet beta cells), while there are some compensatory phenomena(increasing numbers of islets and non-senescent mitochondria).