Chemical induction of sister-chromatid exchanges in human lymphocytes treated in G₀ prior to stimulation by different mitogens and revealed 72 h later in second division cells

Frequencies of sister-chromatid exchanges (SCE) were determined in second-division metaphases of human lymphocytes, exposed for 1 h during the G₀ phase to mitomycin C (MMC) alone or to cyclophosphamide (CP) in the presence of S9 mix. The cells were then cultured for 72 h in the presence of phytohemagglutinin (PHA), concanavalin A (Con A), Wistaria floribunda (WFA) or Lens culinaris (LcH-A) extracts. Large differences in mitotic indices (MI) and cell-cycle kinetics were observed among cells subjected to the various treatments. However, in the controls as well as in the cultures submitted to a G₀ mutagenic exposure, the yield of SCE was not influenced by the mitogenic agent and was, therefore, independent of the proliferation properties of the cultured lymphocyte population.