Daunorubicin reductase activity in leukemia leukocyte homogenates

Daunorubicin reductase activity was estimated in peripheral leukocytes drawn from 23 patients with acute or chronic leukemia. Since the enzyme converts daunorubicin to daunorubicinol, a derivative exposing higher cytotoxic action than daunorubicin, it is important for leukemia treatment to know its leukocyte level. Calculations of reductase levels were based on the presumption that one enzyme unit equals an activity which is producing 1 nanomol daunorubicinol per 1 mg homogenate protein during 30 minutes of incubation. It was found, that blasts of different patients with the same leukemia type displayed different reductase levels, ranging between 11.0 and 74.8 U.