SISTER-CHROMATID EXCHANGES IN HUMAN-LYMPHOCYTES TREATED IN-VITRO WITHCADMIUM IN G(0) AND S-PHASE OF THEIR CELL-CYCLES

Sister chromatid exchanges (SCEs) were analyzed in human phytohemagglu tinin-activated peripheral lymphocyte cultures exposed to varying conc entrations (10(-7)-10(-3) M) of cadmium chloride in vitro at two diffe rent stages of the cell cycle, G(0) and early S phase. When cadmium ch loride was administered at the G(0) phase, no increase in the SCEs wer e observed for the doses 10(-6) and 10(-5) M. Concentrations equal to or larger than 10(-4) M cadmium chloride were lethal to human lymphocy tes in our experimental conditions. A highly statistically significant increase was observed in the SCE frequency with increasing cadmium ch loride concentration (10(-7)-10(-4)) when cadmium was administered at the early S phase, which was 24 h after culture initiation. The increa se in SCE frequency was higher when the cultures were terminated at 54 h: compared to termination at 72 h. In order to examine the effects o f cadmium administered at the S phase on SCE frequency in different in dividuals, 10(-5) M concentration was used and the cultures were termi nated at 54 h after culture initiation. A 2- to 3-fold increase in the SCE frequency was observed in all six individuals examined. A progres sive decrease in the proliferative index was also observed by increasi ng cadmium chloride concentration. These results demonstrate that the genotoxicity of cadmium chloride may be changed depending on the stage of the cell cycle in human lymphocytes. This may be one of the reason s of contradictory findings in the literature. (C) 1998 Elsevier Scien ce B.V.