Using either the routine staining procedure or the Feulgen-like Gautier's method the condensed pattern of hepatocyte chromatin in adrenalectomized rats appeared unchanged 1 hr after cortisol administration, whereas at 4 hr and especially at 8 hr it looked more dispersed, in parallel with an increased synthesis of RNA and nuclear nonhistone proteins (NHP). The quantity of [3H]cortisol bound to deoxyribonucleoproteins (DNP) was the same at 1 and 4 hr after hormone treatment and it was unaffected by amanitin, which induced a chromatin condensation. Eight hours after cortisol injection almost all the DNA structures, revealed by the Gautier technique, were in the unraveled form; concurrently, a large quantity of perichromatin fibrils was visualized with the Bernhard method for ribonucleoproteins (RNP). Amanitin poisoning of 8-hr stimulated rats induced, 1 hr after treatment, a light condensation of the DNA structures and a strong condensation after 2 hr; the perichromatin fibrils were lightly reduced 1 hr after toxin injection and had almost disappeared 2 hr thereafter. Amanitin reduced RNA synthesis to about 25% of control value both 1 and 2 hr after poisoning. No modification of NHP synthesis was observed after toxin treatment. Our results demonstrating a strict relationship only between the chromatin pattern and the quantity of perichromatin fibrils, morphological expression of heterogeneous nuclear (hn) RNA which has been synthesized (J. P. Bachellerie, E. Puvion, and J. P. Zalta,Eur. J. Biochem. 58, 327, 1975; S. Fakan, E. Puvion, and G. Spohr,Exp. Cell Res. 99, 155, 1976), suggest that the chromatin ultrastructural changes induced by cortisol are a consequence and not a cause of gene transcriptional activity. © 1979 Academic Press, Inc.
