Unstable diabetic state produced by a small dose of streptozotocin in rats

A diabetic state was induced with a single intraperitoneal dose (45 mg/kg) of streptozotocin in rats. Their fasting blood glucose concentrations oscillated between 12.7 +/- 1.9 mmol/l and 4.6 +/- 0.6 mmol/l during 35 days of monitoring. Their body weights were also reduced, while controls gained weight, although food consumption was not significantly different. Also, within the first 1/2-hour of the oral glucose tolerance test, blood glucose concentration increased in the diabetic and the control rats, but only in the control rats was there a simultaneous increase in serum IRI concentration (7.2 +/- 8 x 10(2) pmol/l to 27.0 +/- 5.2 x 10(2) pmol/l) which, like the blood glucose concentration, subsequently fell to fasting level in the control rats. In the diabetic rats, however, it was not until the following hour of the tolerance test that serum IRI concentration increased (3.4 +/- 0.3 x 10(2) pmol/l to 65.0 +/- 12.5 x 10(2) pmol/l) and blood glucose concentration began to fall. By the end of the test in the diabetic rats, blood glucose concentration fell but remained significantly higher than the control value. Additionally, no pancreatic tumours were identified in these diabetic rats. The results therefore suggest that an unstable diabetic state was produced by streptozotocin because the threshold for insulin secretion by glucose was increased, while the production of insulin by the pancreas was not significantly affected.