Picrosirius red staining of the lung tissues treated with ZnONP at 150 cm2
/rat. (A) vehicle control; (B) ZnONP at 24 h; (C) ZnONP at 1 wk; (D) ZnONP at 4 wks. Note that collagen deposition (arrow) was increased 1 and 4 wks after instillation of ZnONP. Bar scale: 50μm.