The researchers studied the effects of pirfenidone on lung fibrosis caused by paraquat in mice. They divided the mice into different groups and treated them with different doses of pirfenidone and dexamethasone. They found that the survival rates were higher in the groups treated with dexamethasone and higher doses of pirfenidone. The lung tissue in these groups also had lower levels of hydroxyproline, a marker of fibrosis, compared to the group exposed to paraquat only. This suggests that pirfenidone may have a beneficial effect in reducing lung fibrosis induced by paraquat in mice.