Rat-derived ELT3 cells were subcutaneously injected into female ovariectomized mice implanted with slow-releasing pellets of E2, Pg, E2 + Pg, or placebo. (A) Lung sections from female mice 29 were stained with H&E. (B) Quantification of alveolar air space in mouse lungs from all treatment groups. The area of alveolar space was scored from 30 random fields per lung section. The ratio of alveolar space to the corresponding lung area was calculated and illustrated in a scatterplot. (C) Immunohistochemical staining of CD45 in mouse lung sections. (D) Immunofluorescent staining of SPC in mouse lung sections. *p<0.05, ** p < 0.01, Student t test.