Streptozotocin-induced hyperglycemia is decreased by nitric oxide inhibition

1. Diabetes mellitus type I was induced in 3-month old male C57 BL/KS-mdb mice (N = 24) by ip injection of streptozotocin (STZ, 45 mg/kg body weight) for 5 days. 2. To determine the possible protective effects of nitric oxide inhibition against hyperglycemia, the STZ-diabetic rats received two doses of NG-nitro-L-arginine- methyl ester (L-NAME) (10 mg/kg body weight and 10 mg/mouse) dissolved in PBS for 45 consecutive days. Another group of STZ-treated rats was similarly treated with L-arginine (5 mg/mouse). 3. Blood glucose levels were 118 +/- 37 mg/dl after 8 days of L-NAME administration (10 mg/kg body weight, N = 12) and 186 +/- 22 mg/dl (N = 12) after 5 days of L-NAME administration at the 5 mg/mouse dose. Treatment with L-arginine (5 mg/mouse, N = 12) caused a significant increase in blood glucose level to 151 +/- 17.5 mg/dl, showing the relevance of nitric oxide formation in this type of diabetes. 4. In STZ-diabetic mice treated with L-NAME (N = 12), diuresis was reduced by approximately 58% compared to STZ animals, whereas in L-arginine-treated animals (N = 12) diuresis returned to STZ levels. Urinary protein excretion, which was significantly affected by STZ (123% compared to control) was significantly reduced by 66% after treatment with L-NAME for 45 days, whereas treatment with L-arginine caused a return to STZ values. 5. Urinary kallikrein excretion, which was reduced by 80% in STZ mice compared to control, returned to control levels after L-NAME treatment. 6. The present results suggest a relationship between nitric oxide levels and the reduction of diabetic state and improved renal function by L-NAME.