Effect of streptozotocin on the ultrastructure of rat pancreatic islets.

Our objective was to study the effects of three (30, 40, and 50 mg/kg) doses of Streptozotocin (STZ) on fasting plasma glucose level (FPG) and observe its effects at the cellular level in rat pancreas by electron microscopy. FPG was measured in rats before induction of diabetes and then on 3, 7, and 14 days after induction of diabetes with STZ. Keto diastix urine strips were used to check urine glucose and ketone bodies. Two weeks after the induction of diabetes, the rat pancreas was removed and fixed for light and electron microscopic studies. Three days after induction, the mean FPG level was 112 mg/dl in Group I (30 mg/kg STZ), 217 mg/dl in Group II (40 mg/kg STZ), and 376 mg/dl in Group III (50 mg/kg STZ). Histology was normal in Group I but revealed altered islet structure in Groups II and III. Ultrastructure revealed intact D cells in all three groups. The focal mitochondria and Golgi complex swelling found in A and B cells was occasional in Group I and frequent in Groups II and III. Swelling of other organelles and reduction in the size and number of granules was further observed in Group III. It is our conclusion that the 30-mg/kg body weight STZ produces mild changes while 50 mg/kg proves to be fatal. STZ at 40 mg/kg has a moderate effect on plasma glucose as well as on the islets of Langerhans at a cellular level.