In the chromatin of 24-h regenerating rat livers, derivative melting profiles are characterized by a high proportion of transitions above 90°C. After the injection of diethylnitrosamine there is a rapid shift to lower melting temperatures. This is due to a rearrangement of the chromatin to higher amounts of nucleosomal components but possibly also a consequence of chemical modifications and conformational alterations of the DNA. In the nonregenerating liver essentially the same observations can be made, although reactions proceed significantly slower. These results are in good agreement with the observation that carcinogens are more active in tissues stimulated to rapid proliferation as compared to resting tissues.

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