Induction of 6-thioguanine-resistant mutants and SCEs by 3 chemical mutagens (EMS, ENU and MMC) in cultured human blood lymphocytes.

Human peripheral blood lymphocytes were exposed in vitro to a series of graded concentrations of ethyl methanesulphonate (EMS) or N-ethyl-N-nitrosourea (ENU) or mitomycin C (MMC) to: (a) estimate the frequency of thioguanine-resistant (TGr) cells using the T-cell cloning technique, (b) examine the induction of sister-chromatid exchanges (SCEs) by these chemicals in the lymphocytes of the same blood sample used to study the TGr cells, and (c) assess the nature of correlations between these two biological end-points. The frequencies of TGr cells as well as those of SCEs increased with increasing concentration of the chemicals studied. For EMS and ENU, the increases were consistent with linear dose-effect relationships. There was a linear relationship between SCEs and mutation induction for all 3 chemicals; but the ratio of induced SCEs to induced mutants was different for the different chemicals, being highest for ENU, followed by EMS and MMC, in that order. The basis for these differences is discussed in the light of what is known about the relationships between chemical reactivity patterns and the resultant biological effects of these chemicals.