Radiation-induced Liberation of DNA-protein Complex in Rat Spleen

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Abstract
Male albino rats 6-8 wk old were exposed to 600 R of X-rays. Spleens were excised at 6 h after irradiation, homogenized in ice-cold 0.14 M NaCl, and the homogenate was centrifuged at 4500 g 5 min. The clear supernatant fluid containing free DNA and other macromolecules, such as RNA and protein, was analyzed. Following treatment with formaldehyde, the protein-like molecules were firmly bound to DNA and were no longer dissociable from DNA even in solutions of high ionic strength. The question was whether these protein-like molecules were binding to DNA before formaldehyde treatment; a control experiment was performed. Under these experimental conditions, the artificial binding of DNA to other molecules essentially detached from the DNA does not occur during stabilization of the free DNA with formaldehyde. Free DNA complexed with protein in its native state. The free DNA which is actually a complex of DNA and protein, is a material like DNP [deoxynucleoprotein] rather than chromatin. The DNA released from lymphatic cells after moderate doses of X-irradiation was called free DNA for 19 yr but this free DNA is a sort of DNP and should not be called free DNP. Phenomena including release of free DNA, nuclear pyknosis and interphase cell-death should be reevaluated.