Dose-fractionation sensitivity of mouse kidney clonogens measured using different interfraction intervals and postirradiation assay times.
The fractionation sensitivity of kidney clonogenic epithelial cells (X-irradiation in vivo, assay in vitro) was quantified using the linear-quadratic model. The cells were assayed either immediately after the fractionation schedule or after a time delay in order to compare the relative amounts of dose sparing due to fractionation (conventionally sublethal damage repair) and to post-irradiation delay intervals before assay (conventionally potentially-lethal damage repair). As the delay before assay was increased, there was a tendency for both alpha and beta to decrease, and as a consequence the alpha/beta ratio stayed virtually unchanged (3.3-4.4 Gy) regardless of delay time before assay. No change in survival was observed from 12 h to 6 weeks after neutron irradiation (62 MeVp-->Be), suggesting that the change observed after X-rays was due to repair rather than repopulation. As the interfraction intervals in an 8-fraction X-irradiation schedule were increased in steps from 6 h to 5 days, there was improved survival, consistent with the presence of long-term repair. These studies provide further evidence for the potential importance of long-term repair in late reacting tissues not only during but also after multifraction irradiation schedules.
Jen
Y M
YM
Cancer Research Campaign Department of Experimental Radiation Oncology, Paterson Institute for Cancer Research, Christie Hospital (NHS), Trust, Manchester, UK.
Hendry
J H
JH
D000818:Animals; D016923:Cell Death / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004307:Dose-Response Relationship, Radiation; D004848:Epithelium / Q000473:pathology / Q000528:radiation effects; D005347:Fibroblasts / Q000473:pathology / Q000528:radiation effects; D066298:In Vitro Techniques; D007668:Kidney / Q000473:pathology / Q000528:radiation effects*; D008297:Male; D051379:Mice; D009502:Neutrons; D011829:Radiation Dosage; D013234:Stem Cells / Q000473:pathology / Q000528:radiation effects*; D013997:Time Factors; D014965:X-Rays