Suppression by arsenic trioxide of the induction of mutations in the mouse bone‐marrow and male germ cells by an alkylating agent

Arsenic trioxide at a dose range 1/4–1/40 LD₅₀ has not induced dominant lethals in male mice germ cells and a significant increase of the number of micronuclei in young erythrocytes in the bone‐marrow of mice. But the effective alkylating agent (thio‐TEPA) at a dose 1/10 LDLo has induced an increase of dominant lethals in germ cells and an increase of the number of micronuclei in erythrocytes. After a combined treatment under the same conditions by thio‐TEPA, followed by treatment with arsenic trioxide, one observed a suppression of both the induction of dominant lethals in male germ cells and micronuclei in young erythrocytes of the bone‐marrow. Our data may be interesting, because they show that the combined exposure by two very toxic substances produces a less harmful genetic effect than either one of them separately.