Differences in the action of nitrosomethylurea and streptozotocin.

The biological and metabolic effects of nitrosourea and its alkyl derivative Streptozotocin were compared and it was concluded that the two drugs have different modes of action. This conclusion is based on the following observa tions. Bacteria resistant to Streptozotocin are sensitive to all of the biological effects of nitrosomethylurea, i.e., devitalization, inhibition of cellular metabolism, and degradation of cellular DNA. In bacteria as well as in mammalian cells Streptozotocin is primarily an inhibitor of DNA synthesis while nitrosomethyl urea inhibits all macromolecular processes studied. The nitrosomethylurea-induced devitalization and degrada tion of cellular DNA is blocked by inhibitors of energy metabolism. Such is not the case with streptozotocin-treated cells. There is a fundamental difference in the basis of the resistance of bacterial mutants insensitive to Streptozotocin and nitrosomethylurea respectively.