THE EFFECT OF SILYMARIN - A HEPATOPROTECT IVE SUBSTANCE ON HISTONES IN THE LIVER OF IRRADIATED RATS

Changes of concentration, total content of histones and relative porti ons of histone fractions were investigated in the liver of rats after administration of the hepatoprotective substance silymarin (70 mg/kg) and after gamma-irradiation of the whole body at a dose of 3 Gy, which were examined in 30 hours and in 7 days. Administration of silymarin alone considerably increased the concentration, particularly total con tent of extractable histones in the liver of rats examined in hour 30 (Fig. 1). They decreased below the level of control values after 7 day s. The whole body irradiation at a dose 3 Gy of gamma-radiation caused a steep fall of the concentration and total content of histones in ho ur 30, which persisted also on day 7. Silymarin administered 1 hour be fore irradiation prevented quantitative changes of histones in hour 30 , after irradiation the fall was still steeper than after irradiation without silymarin administration. As Tab. I shows, a significant decre ase in the relative portion of histone fractions H2A + H2B was found i n the extracted histone of the experimental animals of all 3 groups in hour 30, as well as a decrease in the fraction H1 after irradiation w ithout silymarin administration. A decrease in the lysin-rich histone portion was related to an increase in the relative portion of histone H3. In the rats which were administered silymarin 1 hour before irradi ation these changes were found to persist until day 7, and they were r elated to an increase in the subfraction H1-degrees within the histone fraction H1 (Tab. II). Hence the results document that silymarin admi nistration 1 hour before irradiation had a positive effect which was o bserved in all the investigated parameters in hour 30 after irradiatio n. But the radioprotective effect of silymarin was only temporary whil e until day 7 after irradiation histone variations were identical or s till larger than after irradiation without silymarin administration.