The changes and significance of mast cells in irradiated rat liver.

There has been no report on changes in mast cells in hepatic radiation injury. Because of the interactions between mast cells and fibroblasts and mast cell changes in radiation interstitial pneumonitis, we examined the mast cells in experimental hepatic irradiation. We used 60Co gamma-ray in a single dose of 10, 30, 50, and 60 Gy given to the liver area of male Wistar rats. The liver tissue was examined 0.5, 1, 2, 3, 6, 9, and 12 months after irradiation. The mast cells were quantitatively and qualitatively assessed in liver sections by light and electronmicroscopy. Typical chronic liver fibrosis occurred after 30 Gy. As the lesions progressed in severity, the number of mast cells increased and they became larger 1 to 2 months after irradiation. After 3 to 6 months, this change was very marked and degranulation was noted. Both the number and size of mast cells were increased markedly. The peak intensity in mast cell changes paralleled that of connective tissue proliferation. At 12 months, when the fibrous tissue was rich in collagen, the mast cells decreased in number. Our findings suggest that mast cells participate in the development of radiation hepatic fibrosis.