Abstract
1823 Chronic pharmacologic anabolic-androgenic steroid (AAS) treatment using testosterone propionate (TP) has previously been shown to improve the force generating capabilities of the diaphragm muscle of gonadally intact adult male rats without altering cross-sectional area. PURPOSE: The purpose of this study is to determine the effect of AAS treatment on satellite cell activation in the diaphragm muscle. METHODS: Adult male rats (250–275 g initial body weight) were housed in the USC vivarium with food and water supplied ad libium. Serum testosterone levels were elevated to approximately 10x physiologic levels for up to 28 days through the use of subcutaneously implanted Silastic™ capsules filled with crystalline TP. Animals were deeply anesthetized and killed by transcardial saline perfusion followed by 4% paraformaldehyde in situ. The right and left costal diaphragm muscle (DIAm) were harvested and prepared for immunohistochemistry. Immunohistochemical analysis was performed on 10 μm-thick sections utilizing standard protocols. Goat anti-Mcadherin, Santa Cruz, CA (satellite cells), rabbit anti-Laminin, DAKO, Denmark (basal lamina), rabbit anti-MyoD, Santa Cruz, CA, (myogenic regulatory factor) were used to visualize to identify quiescent and activated satellite cells. Nuclei were labeled with DAPI (Molecular Probes, OR). One-way ANOVA with Bonferroni correction was used to determine differences between groups. RESULTS: Significant increases in DIAm quiescent satellite cell number, relative to controls, were observed after 7-days of TP treatment, (39.3 and 16.0, respectively; F = 4.97, p = 0.01). Interestingly, quiescent DIAm satellite cell numbers appear to return to control values after 14 and 28 days of TP treatment. Cross-sectional area (μm2) and number of myonuclei per fiber were not affected by TP treatment (F = 0.45, p = NS, and F = 0.59, p = NS, respectively). CONCLUSIONS: These data suggest that pharmacologic TP treatment transiently increases quiescent satellite cell number. These observations suggest that TP treatment of sedentary adult male rats transiently increases the capability of this muscle to rapidly adapt to physiologic stresses by increasing the number of cells capable of myogenic differentiation. (Research funded by NHLBI: HL-59904 to CEB).
Published Version
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