DNA Synthesis in Irradiated Hair Follicles of the Mouse

>Hair follicles in mice were induced to produce hair by plucking and were then x irradiated with 200, 800, or 3000 rads. DNA synthesis in the proliferating matrix cells of irradiated hair follicles was studied at times from immediately after to 48 hours after irradiation, by the method of labeling with tritiated thymidine and autoradiography. Reduction of thymidine incorporation commences immediately after irradiation and amounts to about 50% within 30 minutes with the two higher doses, possibly also with 200 rads. This is an effect on cells in the process of synthesizing DNA at the time of irradiation. R is followed by a slow decline which may be of complex nature. Resumption of DNA synthesis occurs within 12 hours post-irradiation, even with the highest dose used, and considerably precedes resumption of mitotic activity. (auth)