[The relations between doses of streptozotocin and pathosis in induced diabetes mellitus]

Tail-vein injections of streptozotocin (STZ) in various doses (20-60 mg/kg body weight) were used to induce diabetes mellitus in male rats of the Sprague-Dawley strain. Resulting pathosis was observed on the basis of various parameters (body weight, blood glucose, plasma insulin, glucose-tolerance tests, uroscopy, hemodiagnosis, and skin strength) Results 1. Diabetes mellitus was induced in all rats of the group in which the dosage was STZ 40 mg/kg body weight (S-40 group). Blood-glucose level in this group was about 340 mg (3 times the quantity in controls). Plasma-insulin level was about 8.9 microU/ml (about 1/3 the quantity in controls). Glucose-tolerance tests and observation of urino-glucose showed reductions in glucose tolerance and plasma-insulin response. 2. In the S-40 group, pathosis of induced diabetes mellitus had stabilized 30 days after and persisted for 90 days after STZ injection. 3. Skin strength decreased for 20 days after STZ injection. The level remained stable at half the strength of control skin from 30 to 90 days after the injection. 4. In groups in which doses were STZ 20 mg/kg body weight or STZ 30 mg/kg body weight, diabetes mellitus was induced in some of the rats. The animals tended to recover from the induced pathosis. 5. Diabetes mellitus was induced in all rats to which doses of STZ 50 mg/kg or STZ60 mg/kg body weight were induced. shortly after injection, the induced-diabetes pathosis changed for the worse; and grave complications (hypo-albuminosis, diabetic ketocacidosis, and diabetic proteinuria) were observed. A large number of the rats in these groups died. 6. The results of this study confirm the opinion that STZ 40 mg/kg body weight is the optimum dose for STZ induction of diabetes mellitus in rats for experimental studies. The suitable term for such studies is from 30 to 90 days after STZ injection.