Different modes of action of sodium arsenite, 3-aminobenzamide, and caffeine on the enhancement of ethyl methanesulfonate clastogenicity.

Chromosomal aberrations induced by ethyl methanesulfonate (EMS) in Chinese hamster ovary cells were potentiated by subsequent exposure to sodium arsenite (AS), 3-aminobenzamide (3AB), or caffeine (CAF). The coclastogenicity of AS was most evident when this drug was applied for 3 or 6 h immediately after EMS was removed, whereas caffeine acted primarily after 12-18 h. The coclastogenicity of 3AB was not stage dependent. AS and 3AB increased chromatid exchanges more than chromatid breaks, whereas caffeine mainly increased chromatid breaks. Thus the coclastogenicities of AS, 3AB, and CAF differ in their time of action and the types of aberrations they potentiate.