Sequential morphological changes in pancreatic islets of spontaneously diabetic rats.

This study describes the sequential morphological changes in pancreatic islets from 1-, 6-, and 18-month-old male eSS rats, as compared to aged-matched control animals. Spontaneous diabetes mellitus was confirmed in 6- and 18-month-old eSS rats after an oral glucose tolerance test. Light microscopic immunocytochemical and morphometric techniques were used to study islet-cell populations. The pancreas was normal, and the morphometric methods did not reveal significant changes in islets from 1-month-old rats. However, 6-month-old eSS animals showed disruption of islet architecture and fibrosis in the stroma. The volume density (Vvi) of endocrine tissue and the Vvi and percentage of B cells were increased, whereas the Vvi of exocrine tissue and the Vvi and percentage of A cells were diminished. Eighteen-month-old eSS rats also exhibited conspicuous islet lesions. Nevertheless, the Vvi of endocrine tissue and the Vvi and percentage of B cells were diminished, while the Vvi of exocrine tissue and the Vvi and percentage of D cells were increased. Our results provide further quantitative evidence for the sequential morphological events occurring in the pancreatic islets of a useful animal model of diabetes mellitus.