A quantitative assessment of changes in the dermal fibroblast population of pig skin after single doses of X-rays.

Investigations were carried out into the time- and dose-related changes in the density of fibroblasts in the dermis of irradiated pig skin. The time course of these changes in the density of fibroblast nuclei in the reticular dermis was studied from 6 to 104 weeks after irradiation with a single dose of 15.4 Gy of X-rays. The largest decrease in the number of fibroblasts occurred between 12 weeks and 26 weeks after irradiation; after this time there was only a slight fall in the fibroblast number until 104 weeks when the observations ceased. At 26 weeks and later times after irradiation the reduction in the density of fibroblast nuclei in the reticular dermis was dose-dependent for single doses in the range 8.0-20.7 Gy. The dose-response curve had an initial shoulder, after which the fall in the fibroblast nuclear density was linearly related to dose. Data obtained at other times, between 26 weeks and 104 weeks after irradiation, could be fitted by the same dose-response curve. The fall in the counts of fibroblast nuclei was compared with earlier studies in pig skin. The loss of fibroblasts occurred after an initial reduction in blood flow in the pig skin but was concomitant with the general reduction in dermal thickness.