Apoptosis in growing hair follicles following gamma-irradiation and application for the evaluation of radioprotective agents.

The usefulness of apoptotic fragments assay for investigating the radiation response of hair follicles and evaluation of radioprotective agents was examined in ICR mice. The extent of changes following 100 cGy (1000 cGy/min) was studied at 0, 2, 4, 8, 12, 16 or 20 hours after exposure. The maximal frequency was found 12 hours after exposure. The mice that received 50, 100, 200, 400 or 800 cGy of gamma-rays were examined 12 hours after irradiation. Measurements performed after gamma-ray irradiation showed a dose-related increase in apoptotic cells in each mouse studied. The dose-response curves were analyzed with a linear-quadratic model: the frequency (number per follicle) of apoptotic cells in the hair follicle was y = (0.05527 +/- 0.009574) D + (-0.00001988 +/- 0.00001337) D2 + 0.227 (r2 = 0.964, D = 100 cGy). The frequency of radiation (100 cGy)-induced apoptosis in hair follicles was reduced by pretreatment of diethyldithiocarbamate (DDC, i.p. at 30 minutes before irradiation, p < 0.05) or green tea (i.p. at 12 and 36 hours before irradiation, p < 0.01). From these results, it is thought that this model will be useful in the detection of radiation response and radioprotective agents.