PARACETAMOL-INDUCED SPINDLE DISTURBANCES IN V79 CELLS WITH AND WITHOUT EXPRESSION OF HUMAN CYP1A2

Spindle disturbing effects in terms of c-mitosis and cytotoxicity of p aracetamol were investigated in two Chinese hamster V79 cell lines, on e of which (V79MZh1A2) was transfected with human CYP1A2. This enzyme catalyses the oxidative formation of the reactive paracetamol metaboli te, NAPQI, believed to initiate hepatoxicity by covalent binding to pr oteins after overdose. In the native V79 cell line paracetamol increas ed c-mitosis frequency in a concentration dependent manner from 8.7+/- 3.5% (control) to 66+/-18% at 20 mM. A significant increase to 13.3+/- 3.5% was first seen at 2.5 mM in the native cell line (P<0.05). In the V79MZh1A2 cells the concentration-effect curve was slightly shifted t o the left (P<0.05) with c-mitosis frequency increased to 12.1+/-2.6% (P<0.05) at 1 mM paracetamol. At 5 mM paracetamol the c-mitosis freque ncy was 14.4+/-5.0% and 19.0+/-3.8% in the native and CYP1A2 expressin g cell lines, respectively (P<0.05). At 20 mM paracetamol the c-mitosi s frequency was 61+/-10% in the V79MZh1A2 cells. Cell survival was red uced to approximately 50% at 5-10 mM paracetamol in both cell lines. A t 20 mM paracetamol survival was further decreased to 39+/-9% in V79MZ h1A2 cells only (P<0.05). The present study demonstrated that paraceta mol may disturb the spindle of dividing cells conveying a risk of aneu ploidy. The spindle disturbing effect was only slightly enhanced by ex pression of CYP1A2, suggesting that metabolic activation plays only a minor role in this genotoxic effect. The reduction of survival mirrore d the increase in c-mitosis frequency.