The partial protective effect of the hydroxyl radical scavenger dimethyl urea on streptozotocin-induced diabetes in the mouse in vivo and in vitro.

The protective effect on streptozotocin-induced diabetes of dimethyl urea, a hydroxyl radical scavenger, has been evaluated in vivo and in vitro. Pretreatment with dimethyl urea before a single diabetogenic dose of streptozotocin partially protected NMRI mice from hyperglycaemia, whereas the serum glucose of C57BL/KsJ mice increased during week 2 of observation. When the pancreases of these latter mice were examined histologically, insulitis was found in 15 out of 22 animals. The protective effect of dimethyl urea in the NMRI mice was not due to short-term hyperglycaemia induced by the drug, since pretreatment with glucose did not protect from streptozotocin but potentiated its diabetogenic effect. Dimethyl urea reduced the inhibition caused by streptozotocin on proinsulin biosynthesis of NMRI islets in vitro. It is suggested that streptozotocin-induced diabetes in mice may involve generation of hydroxyl radicals which are toxic to islet B cells. If this immediate cytoxicity is reduced by a scavenger, a more slowly developing hyperglycaemia and an accompanying insulitis may occur in particularly susceptible animals.