Effects of streptozotocin in the male guinea pig: A potential animal model for studying diabetes

The effects of acutely administered streptozotocin in the male guinea pig were studied for a period of 18 days following treatment. A single intracadiac injection of streptozotocin (150 mg/kg) was administered on Day 0. On Day 2, plasma glucose concentrations were not significantly different from control levels. On Day 7 and 18, an oral glucose tolerance test was performed with streptozotocin-treated animals receiving an acute injection of either insulin (18 U/kg, i.m.) or saline 90 minutes prior to glucose loading. On Day 7, streptozotocin-treated animals receiving saline had significantly elevated plasma and urine glucose concentrations at 3 hours after glucose loading when compared to controls. Streptozotocin-treated animals receiving insulin however, had significantly lower plasma glucose concentrations at 3 hours while urinary glucose was equal to control values. The second glucose tolerance test performed on Day 18 yielded similar results. Necropsies were performed on animals that died after Day 6. Lesions found in the streptozotocin-treated animals included: 1) small and irregular pancreatic islets, pyknotic nuclei and degranulation of beta cells, 2) renal proximal tubule swelling and vacuolization, 3) adrenal cortical hyperplasia, 4) hepatocyte vacuolization, and 5) visceral fat atrophy. Animals surviving until Day 18 were sacrificed and found to have significantly elevated kidney and adrenal weights compared to controls. These changes illustrate the effectiveness of streptozotocin in the acute chemical induction of diabetes in an animal model (guinea pig) which, like humans, requires a dietary source of ascorbic acid.