[Study of the changes in rat liver chromatin after hydrocortisone administration]

After hydrocortisone administration some properties of rat liver chromatin were studied by means of melting technique and circular dichroism. Hydrocortisone caused a more than 2.5-fold increase in amount of the chromatin active fraction. Distinct differences were detected between circular dichroism spectra of total chromatin and of its active fraction as well as between differential curves of the chromatin active fraction melting in control and test samples. The difference was expressed as a decrease in temperature of melting in a low-point zone and as appearance of the secondary maxima in the region of nucleosomes melting. These data suggest that the decondensation of nucleosome-containing sites takes place which is considered as an indirect evidence of the chromatin activation.