A Study on UVI - induced DNA Synthesis in Mouse Skin in Vivo Studied by Autoradiography

Shin, Jun Woo; Kim, Kyu Han; Youn, Jai Il

Abstract

The status of DNA synthesis and the effect of UV radiation on the DNA synthesis were studied in mouse skin by microautoradiography. Mice exposed to 100mJ/cm of UVB were injected intradermally with tritiated thymidine, 5 minutes, 2, 6 and 24 hours after irradiation and biopsies were processed for light microscopic autoradiography, A total of 25 ICR female albino haired mice were used as subjects. We compared heavily labeled cells(>10 grains/nucleus) and sparsely labeled cells (3-10 grains/nucleus) in UVL irradiated skin with nonirradiated control skin. 1. Within 5 minutes after UVL exposure an apparent depression in the number of heavily labeled cells occurred. This reduction was statistically significant and remained so for at least six hours post,irradiation. By 24 hours after UVL exposure, the reduction was recovered to nearly control level. 2. By five minutes after UVL exposure, sparsely labeled cells were observed in basal cell layer and differentiated cell layer. The nurriber of sparsely labeled cells appeared highest at five minutes after UVL exposure and then tended to fall to nearly control level at 24 hours. This aberrant type of TdR H incorporation is thought to represent unscheduled DNA synthesis to repair pyrimidine dimers formed in UVL injured DNA molecules,