A comparative study of the clastogenic activity of ethylating agents

The comparative clastogenic effects of six ethylating agents, namely N-ethyl-N-nitrosourea (ENU), N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG), diethyl sulphate (DES), ethyl methane sulphonate (EMS), epichlorohydrin (ECH) and ethylene dibromide (EDB) have been determined in cultured Chinese hamster ovary (CHO) cells. The relative order of potency of the six ethylating agents for the induction of chromosome aberrations related to exposure concentration was ENNG greater than ECH greater than ENU greater than EDB greater than DES greater than EMS with each agent inducing aberrations over a discrete concentration range. In the case of monofunctional agents, ENNG, ENU, DES and EMS there was a relationship between the induction of chromosome aberrations with the Swain-Scott S-value and O-alkylation with those agents with the lowest S-value and the highest proportion of O-alkylation producing chromosome aberrations at the lowest exposure concentrations.