The kinetics of cellular recovery in exponential and plateau growth phase human glioma cells following γ-irradiation

• Published in: International journal of radiation oncology, biology, physics Vol. 30; no. 2; pp. 383 - 390
• Main Authors: Heller, Dennis P., Raaphorst, G.Peter
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 30.09.1994; Elsevier
• Subjects: Biological and medical sciences; Cell Cycle; Cell Division - radiation effects; Cell Survival - radiation effects; Gamma Rays; Glioma - pathology; Glioma cells; Humans; Medical sciences; Photoradiation therapy and photosensitizing agent; PLDR; Recovery half-time; Recovery kinetics; SLDR; Treatment with physical agents; Treatment. General aspects; Tumor Cells, Cultured; Tumors; SLDR; Recovery half-time; Recovery kinetics; Glioma cells; PLDR; Human; Cell proliferation; Nervous system diseases; Radiosensitivity; Malignant tumor; In vitro; Malignant glioma; Ionizing irradiation; Gamma irradiation; Radiobiology; Central nervous system disease; Cell cycle; Established cell line; Kinetics; Repair
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/0360-3016(94)90018-3

Purpose : In this study the kinetics of recovery following irradiation was examined in a human glioma cell line. Specific objectives were: to determine whether recovery is mono- or biexponential in nature; to determine if recovery half-times are different in exponential and plateau growth phase cells; to compare recovery half-times as a function of dose or recovery levels; and finally, to compare the kinetics of sublethal damage recovery and potentially lethal damage recovery in plateau growth phase cells. Methods and Materials : U-87MG cells were irradiated in exponential and plateau growth phases and then subjected to incubation at 37°C for various periods of time following or between doses prior to assaying for survival. Survival recovery curves were fit to a sum of exponential terms. Results : Potentially lethal damage recovery was monoexponential in both exponential and plateau growth phase cells and occurred at the same rate when isorecovery values were compared. Recovery half-times increased in an exponential manner within the observed dose range. Recovery between doses of radiation (sublethal damage recovery) proceeded at a slower rate than recovery following a single dose of radiation (potentially lethal damage recovery). Conclusions : This study suggests that potentially lethal damage recovery is a saturated process and that the recovery half-time may increase in a linear-quadratic exponential function of dose similar to the absolute recovery level. In addition, if iso-recovery levels are compared, the recovery half-time is similar in rapidly and slowly proliferating cell populations.