Changes in nucleoid viscosity following X-irradiation of rat thymic and splenic cells in vitro.
Unscheduled DNA synthesis (UDS) suggested a higher DNA repair capacity of X-irradiated rat thymic (T) cells when compared to splenic (S) cells (Tempel 1980). In the present investigations, damage and repair of DNA supercoiling was measured in T- and S-cells following X-irradiation in vitro by using the nucleoid sedimentation technique and a simplified low-shearing viscometric test. - X-irradiation resulted in a dose (0.6-19.2 Gy) - dependent reduction in sedimentation and viscosity of nucleoids. Within a post-irradiation period of 30-45 min after a challenge dose of 19.2 Gy, DNA repair was accompanied by an increase in nucleoid sedimentation and viscosity in T-cells by about 60 and 300, in S-cells by almost 40 and 100%, resp. The increase in nucleoid viscosity within a 30 min repair period could be reduced in a concentration-dependent manner by DNA polymerase - inhibitors and proteinase K. - The higher DNA repair capacity of T-cells as reflected by UDS is confirmed therefore by the nucleoid characteristics. Apart from this suggestion, measuring nucleoid viscosity may be considered as a sensitive, simple and rapid device to detect radiation-induced DNA supercoiling phenomena.
Tempel
K
K
Arbeitsgruppe Radiologie im Institut für Pharmakologie, Toxikologie und Pharmazie, Tierärztlichen Fakultät, Universität München, Federal Republic of Germany.
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism / Q000528:radiation effects; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects*; D004278:DNA, Superhelical / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D019286:Endopeptidase K; D005260:Female; D008214:Lymphocytes / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D019384:Nucleic Acid Synthesis Inhibitors; D051381:Rats; D011919:Rats, Inbred Strains; D012697:Serine Endopeptidases / Q000378:metabolism; D013154:Spleen; D013601:T-Lymphocytes / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D014783:Viscosity
D004278:DNA, Superhelical; D019384:Nucleic Acid Synthesis Inhibitors; D004259:DNA-Directed DNA Polymerase; D012697:Serine Endopeptidases; D019286:Endopeptidase K