Epilation in mice after single and multifractionated irradiation.
The response of the resting (fully formed) hair follicle to irradiation was studied using an arbitrary 6 unit scale of epilation as an endpoint. Dose-response curves for single and multifractionated irradiations were analyzed in terms of the dose that gave a certain response in 50% of the mice (HRD50). HRD50 values increased with decrease in dose per fraction even when changing from 1.6 Gy to 1.15 Gy per fraction. The plots of the reciprocal of isoeffective doses versus dose per fraction are nonlinear suggesting either inappropriateness of the linear-quadratic model over the whole range of doses, or incompleteness of repair given as they were, at 3-h intervals. Allowing for incomplete repair, estimates for the alpha/beta ratio were 3.1 Gy and 1.7 Gy for the complete data set or for doses less than 7 Gy, respectively. The steep slope of the isoeffect curve plotting total dose versus dose per fraction was comparable to late responding normal tissues like lung, kidney and spinal cord. Such a response is consistent with slow proliferation of the matrix cells of resting follicles. The same animals were kept to assess the effect of dose fractionation on lethal injury to the lung. Since epilation occurs well before death from lung injury, the data for the two responses were correlated to determine whether epilation might help in predicting the probability of the later development of lung injury: no association was found.
Vegesna
V
V
Department of Radiation Oncology, UCLAMedical Center 90024-1714.
Withers
H R
HR
Taylor
J M
JM
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006197:Hair / Q000528:radiation effects*; D008168:Lung / Q000528:radiation effects; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H