Enhancement of pulmonary metastasis of murine fibrosarcoma NR-FS by ozone exposure.

The effects of ozone exposure on the metastasis of a fibrosarcoma (NR-FS) that arose spontaneously in a C3H/He mouse was studied. Male C3H/He mice were exposed to 0.8, 0.4, 0.2, and 0.1 ppm ozone for 1, 3, 5, 7, and 14 d. After the exposure periods, the mice were infused intravenously with NR-FS cells. At 2 wk postinfusion, the lungs were examined for colony development of metastasis. A significantly higher rate of pulmonary metastasis than that of normal mice was observed in the ozone-exposed mice. The enhancement of metastasis due to ozone exposure varied with length of exposure and concentration of ozone. When 1 X 10(5) cells of NR-FS were injected into the tail veins of mice, the maximal enhancement (459%) of pulmonary metastasis was observed in the mice exposed to 0.8 ppm ozone for 1 d. A longer period of exposure to 0.8 ppm ozone also enhanced pulmonary metastasis, although the prolonged exposure (14 d) gradually suppressed the enhancement (268%). In the mice exposed to the lower concentration of ozone, a lower rate of the lung matastasis was observed; even in the mice exposed to 0.1 ppm ozone for the period of from 1 to 14 d, a significantly higher rate of metastasis than that of nonexposed mice was observed.