Synergistic action of leukemogenic agents.

Ionizing radiations (4), carcinogenic hydrocar bons (12), and estrogenic hormones (8) are leuke mogenic for mice of specific genetic constitutions (8). Synergistic and additive effects of x-rays and methylcholanthrene have been demonstrated (1, 13). A preliminary paper has been published on the synergistic action of x-rays and an estrogenic hormone (9). In the present report genetic requirements for synergism are considered, and the synergistic ac tion of estrogenic hormone and a carcinogenic hydrocarbon is demonstrated.