A morphologic and biochemical study of the transcriptional changes in rat liver during the acute inflammatory...

Transcriptional activity in nuclei isolated from the liver of rats during the acute inflammatory reaction induced by a 24-hour treatment with turpentine was evaluated by biochemical and ultrastructural techniques. This experimental model was chosen because it is known to induce an increase in hepatic synthesis of several plasma proteins called acute phase reactants. Using an in vitro system for estimating the activity of RNA polymerases A and B as an approach to evaluate RNA synthesis, we have shown that the activity of enzyme A (responsible for pre-rRNA synthesis) was significantly enhanced, whereas the activity of enzyme B (responsible for giant heterogenous RNA synthesis) remained unchanged in treated rats compared with control rats. At the electron microscopic level, using the Miller technique to spread the nuclear contents, the non-nucleolar transcription units were similar in treated and control rats. In contrast to control rats, more nucleolar transcription units were vizualized in treated rats, although the ribonucleoprotein fibrils were less numerous; in addition, in the latter group 10 to 15 times more aggregates constituted of ribonucleoprotein fibrils and particles were observed, the morphology of which was in agreement with a nucleolar origin. These results suggest that, during the acute inflammatory reaction, there was no overall increase in giant heterogenous RNA synthesis, whereas an increase in rRNA synthesis might be observed.