Study of the response of superoxide dismutase in mouse organs to radon using a new large-scale facility for exposing small animals to radon.

We examined dose-dependent or dose rate-dependent changes of superoxide dismutase (SOD) activity using a new large-scale facility for exposing small animals to radon. Mice were exposed to radon at a concentration of 250, 500, 1000, 2000, or 4000 Bq/m(3) for 0.5, 1, 2, 4, or 8 days. When mice were exposed to radon at 2000 day•Bq/m(3), activation of SOD activities in plasma, liver, pancreas, heart, thymus, and kidney showed dose-rate effects. Our results also suggested that continuous exposure to radon increased SOD activity, but SOD activity transiently returned to normal levels at around 2 days. Moreover, we classified the organs into four groups (1. plasma, brain, lung; 2. heart, liver, pancreas, small intestine; 3. kidney, thymus; 4. stomach) based on changes in SOD activity. Thymus had the highest responsiveness and stomach had lowest. These data provide useful baseline measurements for future studies on radon effects.