Fig. 4
Silver-enhancing and hematoxylin-eosin-stained terminal bronchioles of Sprague–Dawley rat lungs showing no signals in air control at 24 h and 7 days (Panels a & c). In Panel b, a few black silver particles are deposited on the surface of epithelial cells (arrow) at 24 h after 28 μg AgNPs inhalation. In Panel d, more visible agglomerated black silver positivity were observed on the luminal surface and on surface epithelial cells (arrows) and subepithelial connective tissue (arrow heads) at 7 days post-8 μg AgNPs inhalation (internal scale bar = 20 μm for all)