Inhibition of urethane-induced pulmonary adenomas by inhaled plutonium-239.

Abstract Exposure of inbred mice belonging to an A strain to the inhalation of plutonium dioxide significantly inhibited the capacity of urethane to induce pulmonary adenomas, but tumour size was unaffected. Cell kinetic studies suggested that proliferation of cells comprising the adenomas diminished with time, though the decrease was less evident in irradiated than in non-irradiated animals. Alpha irradiation may act by interfering with the immuno-depressive effect of urethane.