Figure 2

Micronucleus-forming activity of organotin(IV) carboxylates following 24-h exposure of MCF-7 cells. Cells were seeded as 3-ml aliquots (≈ 1 × 10⁴ cells) into 30 mm Petri dishes as described in Materials and methods. Following exposure the cells were blocked at cytokinesis by addition of fresh medium containing 2 μg cytochalasin B/ml. Cells were cultured for a further 24 h prior to fixation and staining with 5% Giemsa. Micronucleus formation was scored in 1,000 binucleate cells. In a corresponding control experiment, 1 μM benzo[a]pyrene induced a score of 255 micronucleated and 466 (the distribution being 135, 71, 28, 14, 7) total number of micronuclei in 1,000 binucleate MCF-7 cells. This compared to levels in vehicle control cells of 149 micronucleated and 219 (the distribution being 101, 30, 15, 2, 1) total number of micronuclei in 1,000 binucleate MCF-7 cells.