Streptozotocin is widely used to induce diabetes in laboratory animals through multiple low-dose or single high-dose intraperitoneal injections. HPLC analysis has shown that the composition of the solution may change considerably during the first 2 h after dissolution due to equilibration of the 2 anomers (alpha and beta) of streptozotocin. Because of the drug's alleged instability in solution, the typical recommendation is to administer streptozotocin within 10 min after dissolution. We compared the induction of diabetes in NOD/SCID mice by injection of a single high dose of freshly made or anomer-equilibrated streptozotocin solution. Solutions were prepared from dry compound containing 85% of the alpha anomer, which is the more toxic of the 2. Body weight and nonfasting blood glucose levels were measured weekly for 8 wk. Both solutions induced long-term hyperglycemia, but blood glucose levels and mortality were higher and damage to pancreatic islands more pronounced in the mice receiving freshly prepared solution. A small proportion of mice did not respond in both treatment groups. If stored at 4 degrees C in the dark, the anomer-equilibrated solution retains its biologic activity for at least 40 d; under those conditions the streptozotocin content decreases by 0.1% daily, as determined by HPLC. Anomer-equilibrated streptozotocin solution has several practical advantages, and we recommend its use as standard for the induction of experimental diabetes because this practice may improve reproducibility and comparison of results between different laboratories.
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