Unterschiede zwischen Milz-und Thymuszellen der Ratte in der Wirkung von Ethidiumbromid auf die unprogrammierte DNA-Synthese (DNA-Reparatursynthese) und die Nucleoidsedimentation / Differences between Rat Splenic and Thymic Cells with Respect to the Effects of Ethidium Bromide on the Unsheduled DNA Synthesis (DNA Repair Synthesis) and the Nucleoid Sedimentation

Abstract

To get further insight into the causes of differences between rat splenic and thymic cells with regard to DNA repair synthesis, scheduled (SDS) and unscheduled (UDS) DNA synthesis as well as nucleoid sedimentation of the cells were investigated under the influence of ethidium bromide (EB, 1 -1000 μg/ml). - At concentrations of ≳ 25 μg/ml, EB inhibited SDS of both cell species and UDS of thymic cells; much higher additions of the drug (>200 μg/ml) were needed to diminish UDS of splenic cells, lower EB-concentrations (25- 175 μg/ml) stimulating the UDS of the splenic cell preparation. - The sedimentation rate of splenic and thymic cell nucleoids within neutral sucrose gradients had a biphasic dependence on the EB-concentrations. As compared to thymic cells however, preincubation of splenic cells with 50-250 μg EB/ml resulted in a significant greater (15-30 percent) sedimentation distance. - The results suggest that a relation­ship exists between the stimulation of UDS and the ability of cells to establish a greater DNA compactness in the presence of EB.