Morphometrical and biochemical differences of endocrine pancreata between spontaneously hypertensive and normotensive rats with or without neonatal streptozotocin-induced diabetes.

We studied the morphometrical and biochemical changes of endocrine pancreata in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) with or without noninsulin-dependent diabetes mellitus induced by neonatal streptozotocin (STZ) treatment at 4 months of age. Female (2-day-old) neonates were intraperitoneally injected with 62.5 or 75.0 mg/kg of STZ for SHR, 87.5 or 100.0 mg/kg of STZ for WKY, and vehicle for control. In STZ-treated groups, overt hyperglycemia developed in SHR with significantly decreased serum immunoreactive insulin (IRI), whereas in WKY, hyperglycemia was very mild and serum IRI was not lowered. The number and mean size of pancreatic islets did not differ between SHR and WKY, although mean islet size was reduced by half in both compared with that in the corresponding control, respectively. Percentage distribution of insulin-positive B cells in the islet was significantly reduced more in SHR than in WKY (34% of control versus 64% of control, p less than 0.05). Furthermore, pancreatic IRI content was far more reduced in SHR than in WKY (3% of control versus 43% of control, p less than 0.001). In vehicle-treated groups, the glycemic levels and the morphometrical islets did not differ between SHR and WKY. However, serum IRI was significantly lower but pancreatic IRI content was higher in SHR than in WKY. The mechanisms of strain differences between SHR and WKY seen in the present study were discussed.