An ultrastructural study on the pancreatic islet B cells in diabetic herbivorous voles.

An ultrastructural study was performed on the pancreatic islet cells of normal herbivorous voles and of voles in which diet-induced diabetes had been induced by feeding a low-fibre, high-concentrate diet. Examination of the pancreatic islet cells revealed degranulation and a well-developed Golgi apparatus and rough endoplasmic reticulum in the B cells of the slightly diabetic voles showing moderate hyperglycaemia and hyperinsulinaemia, and markedly degenerative B cells with almost complete absence of secretory granules in the severely diabetic voles showing marked hyperglycaemia and hypoinsulinaemia. These results indicate that the pancreatic B cells had become hyperfunctional so that insulin secretion was increased in the slightly diabetic voles; thereafter the B cells degenerated rapidly and the voles fell into insulin deficiency.