Figure 4.

Effect of testosterone supplementation on satellite cell proliferation in young skeletal muscle 2 and 4 days postinjury. Hematoxylin & Eosin staining of the tibialis anterior muscle 2 days postinjury (A). Representative image showing BrdU (green) and neural cell adhesion molecule (NCAM; red) staining (B). Testosterone supplementation restored the number of BrdU⁺/NCAM⁺ satellite cells, indicating a positive effect of androgens on satellite cell activation and/or proliferation in the young skeletal muscle 2 days postinjury (C). As in aged mice, castrated mice showed a trend toward reduced number of proliferating satellite cells, a deficit rescued by testosterone administration 4 days postinjury (D-E). The number of BrdU⁺/NCAM⁺ satellite cells per unit area did not differ significantly between controls and testosterone-treated orchiectomized mice in figures C and E. Nuclei were counterstained with 4′,6′-diamidino-2-phenylindole (blue). In (B) and (D), arrows indicate BrdU⁺/NCAM⁺ satellite cells. Results are means ± S E M (n = 4 per group).