ALPHA-PARTICLE-INDUCED P53 PROTEIN EXPRESSION IN A RAT LUNG EPITHELIAL-CELL STRAIN

Other investigators have shown that both sparsely ionizing and UV radi ation cause cell cycle arrest that is associated with increased expres sion of wild-type p53 protein. The effect of exposure to alpha-particl es from Pu-238 on the induction of the p53 protein has now been examin ed in cultured lung epithelial cells derived from male F344 rats. The number of cells having increased levels of p53 protein was determined by flow cytometry after the cells had been stained with a monoclonal a ntibody to p53. alpha-Particle irradiation caused a dose-dependent inc rease in p53 protein levels detectable at doses as low as 0.6 cGy, wit h no evidence of a threshold. An increase in p53 protein also occurred in X-irradiated cells. However, no increase was seen in cells exposed to less than 10 cGy of X-rays, indicating the existence of a relative ly higher DNA damage threshold for sparsely ionizing radiation. In add ition, more cells exposed to low doses of alpha radiation had increase d p53 protein levels than would be predicted based on the number of nu clei expected to be traversed by an alpha-particle, suggesting that al pha-particles cause genetic damage by mechanisms in addition to direct interactions with DNA.