"Streptozotocin is widely used to induce Type-1 DM in animal models, such as rats and mice. A single dose of 50 mg/kg body weight in a rat will cause necrosis of β cells followed by β-cell loss and atrophy of the islets."

https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/streptozotocin#:~:text=Streptozotocin%20is%20widely%20used%20to,and%20atrophy%20of%20the%20islets.

Thank you very much for your answer. But since beta cells are necrosed, insulin can no longer be produced and blood glucose level rise, why do animals go into hypoglycemia?

"Fatal hypoglycemia after STZ injectionSome animals die quickly after STZ treatment due to massive islet β-cell necrosis and a sudden release of insulin that results in fatal hypoglycemia, usually within 48 hr of STZ injection."

https://currentprotocols.onlinelibrary.wiley.com/doi/full/10.1002/cpz1.78#:~:text=Fatal%20hypoglycemia%20after%20STZ%20injection,48%20hr%20of%20STZ%20injection.