Intraperitoneally administered streptozotocin (100 mg. per kilogram) produced hyperglycemia (higher than 200 mg. per 100 ml.) in 100 per cent of C57BL, but in none of KK mice. Pretreat-ment with phentolamine (50 mg. per kilogram), an α-adrenergic blocking agent, decreased resistance of KK mice to the diabetogenic action of streptozotocin. On the other hand, pre-treatment with propranolol (10 mg. per kilogram), a β-adrenergic blocking agent, induced resistance to streptozotocin in C57BL mice. This effect of propranolol was potentiated by administration of epinephrine (1 mg. per kilogram).
These findings suggest that the α-adrenergic system protects pancreatic β cells from cytotoxic action by streptozotocin, indicating a predominance of the α-adrenergic system in diabetic mice of the KK strain.