PCA plots (after ANOVA p < 0.01) after normalization of the polar fraction of HepG2 cells analyzed by 1H NMR and pre-processed and aligned using a program developed in-house. A: Spheres with the same colour are technical replicates of the same sample per passage number. For denotation of the colours, see legend to Figure 3. B: Samples re-grouped with regard to treatment (irrespective of passage number). DMSO: green; TCDD: red..