INTER-LABORATORY CALIBRATION PROGRAM FOR THE MOUSE MICRONUCLEUS TEST

The micronucleus test on mammalian bone marrow is widely accepted as a ''screening'' test for chromosome anomalies induced by clastogenic ag ents. The frequency of micronucleated polychromatic erythrocytes (MNPC Fs) in the bone marrow of mice treated with cyclophosphamide (CP), ble omycin (BLEO) and benzidine (BZN) was determined in three different la boratories. Although dic experiments were conducted independently, the results were quite similar for all three laboratories. The mean MNPCE frequencies induced by CP and BLEO were not statistically different. Only for the group treated with a single BZN dose were the mean freque ncies statistically different between laboratories two and three. The homogeneous results obtained by the three laboratories for the micronu cleus test indicate the efficacy of the method and its applicability f or the identification of clastogenic agents.