Figure 2. Differences between testicular FOXO4 expression in young (< 30 years old) and old (≥ 65 years old) men. (A, B) Western blotting revealing no significant difference in FOXO4 protein levels between young and old men (n=6). (C) Immunofluorescent staining showing that FOXO4 localizes predominantly in the cytoplasm of Leydig cells in young men, but in the nucleus in old men. Scale bar: 40 μm. (D) Immunofluorescent staining of FOXO4 and the rate-limiting testosterone synthetic enzyme 3β-HSD showing that nuclear-FOXO4+ Leydig cells express less 3β-HSD than nuclear-FOXO4- Leydig cells in testes from the elderly. Scale bar: 50 μm. Data depict the mean ± SD. NS, nonsignificant, *P<0.05.