Differential persistence of chromosomal damage induced in resting rat-liver cells by X-rays and 4.2-MeV neutrons.
Rats were exposed to 400 rad X-rays or 100 rad 4.2-MeV neutrons and subjected to partial hepatectomy at 1 day, 1 week, 1 month or 3 months after irradiation. 2 or 3 days later the remaining liver was perfused and isolated hepatocytes were screened for micronuclei in the cytoplasm. Frequencies of micronucleated hepatocytes following X-irradiation decreased with increasing time intervals after irradiation, the frequency at 3 months being not significantly different from the control value. Following neutron irradiation, frequencies of micronuclei remained constant at all time intervals tested. In the case of X-irradiation, the progressive decrease in frequencies of micronuclei may be explained by 2 mechanisms operating simultaneously: (i) slow long-term repair of chromosomal damage and (ii) mitotic selection against cells carrying substantial amounts of chromosomal damage. Both mechanisms do not seem to operate in the case of neutron irradiation. For both types of radiation, the dose-effect relationship was linear in the ascending part of the dose-effect curves. The dose-effect curve plateaud at 400 rad X-rays and 50 rad neutrons. The RBE value for 4.2 MeV neutrons in the ascending part of the dose-effect curves was about 4.
D000818:Animals; D002875:Chromosomes / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D008099:Liver / Q000648:ultrastructure*; D008115:Liver Regeneration / Q000528:radiation effects; D008297:Male; D009502:Neutrons; D051381:Rats; D011919:Rats, Inbred Strains / Q000235:genetics; D012062:Relative Biological Effectiveness; D014965:X-Rays