Influence of age on the sensitivity of the rat to streptozotocin.

The relationship between age and sensitivity to the diabetogenic effect of streptozotocin was investigated. Changes in the serum levels of several parameters (glucose, immunoreactive insulin, lipids), as well as changes of the pancreatic insulin content were monitored at 2, 4, 8, 24 and 48 h after the intravenous administration of different doses of streptozotocin in rats of various weights. Different concentrations of blood glucose and lipid and different amounts of pancreatic immunoreactive insulin could be found in rats of different ages 24 and 48 h after injection of the same dose of the drug (in mg/kg body weight). Also, age-dependent changes of serum immunoreactive insulin could be observed as early as 4 h after streptozotocin administration. All these changes indicate that the sensitivity of the rat to the diabetogenic effect of streptozotocin is inversely related to the age of the animals. Most likely, age-dependent pancreatic factors have an important role. In fact, the changes of the minimum dose of streptozotocin required to cause diabetes in rats of different weights closely parallel the age-related changes of the total immunoreactive insulin content of the pancreas of the intact rats. The role of other age-related factors which may influence the effectiveness of streptozotocin action is briefly discussed.