No cyclosporin-induced chromosomal aberrations in human peripheral blood lymphocytes in vitro

Continuous in vitro treatment of human peripheral blood lymphocytes with cyclosporin A for 20 h and 44 h in the absence of metabolic activation decreased the mitotic index in a concentration-dependent way (MI about 35% at 50 micrograms/ml). In the presence of 10% S9 lymphocytes were exposed to cyclosporin A at concentrations which formed cloudy suspension, i.e., above 100 micrograms/ml. A 2 h treatment in the presence of metabolic activation showed a depression of the mitotic index at the 44 h fixation time only. Based upon results concerning the depression of the mitotic index, slides of the 5, 10, 25 and 50 micrograms/ml (-S9, 20 h and 44 h continuous treatment) and 5, 150, 250 and 300 micrograms/ml (+S9, 2 h pulse treatment) treatment groups were selected to be analyzed in the chromosomal aberration assay. At no concentration and at no fixation time did cyclosporin A increase the frequency of cells with chromosomal aberrations.