RADIATION BIOCHEMISTRY OF THE CHICKEN-EMBRYO - DNA-SYNTHESIS AND DNA-DEGRADATION FOLLOWING X-IRRADIATION

Chicken embryos were X-irradiated with a dose of 8 Gy. At a developmen tal stage of 15 days, desoxyribonucleic acid (DNA) synthesis, nucleoid sedimentation, viscosity of the alkaline cell lysates and DNA fragmen tation were examined in brain and/or liver cells. Further studies aime d at the appearance of acid-soluble nucleic acid metabolites in the al lantoic fluid. Complementary investigations comprised the in vitro act ivities of a DNase I and a DNase II of liver and brain cells as well a s of the allantoic fluid of X-irradiated embryos. It could be shown fo r the first time that, following acute X-irradiation of the chicken em bryo, the inhibition of DNA synthesis is accompanied by at least two e nzymatic DNA degradation phases. The early phase comprises a period of 6(-12) h, whereas the second phase lasts, with organ-specific peculia rities, greater-than-or-equal-to 24 h. During the early period, some a poptotic phenomena are seen, whereas at the later stages of radiation response signs of necrolysis become evident. The excretion of DNA meta bolites, probably oligonucleotides, in the allantoic fluid is enhanced following X-irradiation > 2 Gy and may be used as an additional param eter of the overall radiation damage. Therefore, the chicken embryo ma y be regarded as a radiobiological and possibly toxicological alternat ive to laboratory animals with respect to the nucleic acid metabolism.