Effect of lung irradiation on mice following paraquat intoxication.

To determine the effect of lung irradiation in mice with paraquat poisoning and whether irradiation could prevent lung destruction, we found the the lethal dose for 50 percent survival (LD50) in 50 mice (Swiss strain) was 25 mg/kg of body weight. The first control group comprised 15 mice and their lungs were irradiated with 200 rad for seven days. There was no death within six weeks. The lungs at autopsy appeared mildly congested. The control group comprised 15 mice. They were injected with 25 mg/kg of paraquat. Six died within three days. The experimental group included 14 mice injected with paraquat and with lung irradiation. Eight died within three days (p greater than 0.5). The pathologic findings in the experimental group revealed lung congestion and fibrosis that was more pronounced than in the group that received only paraquat. We conclude that radiotherapy is not effective in amelioration of paraquat-induced lung damage in mice.