Figure 3. Acute exposure to Br₂ induces lung emphysematous changes.

Male C57BL/6 mice were exposed to air or Br₂ gas (400 ppm, 30 minutes) and then returned to room air. On days 7, 14, or 21 after Br₂ exposure, mouse lung compliance was assessed by the slope of the deflation limbs of pressure-volume (PV) curves. Br₂ inhalation increased lung volumes as indicated by shifting up and left of PV curves on days 14 and 21 after exposure (n = 5–9) (A). The staining of peripheral lung tissue with hematoxylin and eosin (H&E) showed airspace enlargement (B) and increased alveolar mean linear intercept (L_m) (n = 5). Scale bars are 100 µm. (C) on days 14 and 21 after exposure. Characteristic images are shown. Finally, plasma elastase levels (n = 6–10) (D) and BALF elastase activity (n = 7–14) (E) were elevated in Br₂-exposed mice on days 14 and 21 after exposure. Values are means ± SEM. *P < 0.05 versus air-exposed C57BL/6 mice by 1-way ANOVA followed by Tukey’s post hoc test. PV curves were analyzed by 2-way ANOVA with Bonferroni’s post hoc test.