Mouse Tibialis Anterior Muscle Mass and Androgen Receptor (AR) expression with Testosterone Manipulation

Abstract

PURPOSE: Androgens have a potent effect on muscle mass and protein synthesis regulation. The mechanism by which they act is not well understood. One possible regulator of androgen action is through the androgen receptor (AR). Although the rat has proven to be an important model for androgen action in muscle, less is understood in the mouse. Testosterone dose, type and duration of administration are critical variables for establishing a model of androgen action. The purpose of this study was to determine the effect of androgen manipulation on muscle mass and AR expression after 42 days of anabolic steroid administration on the mouse tibialis anterior (TA) muscle. METHODS: C57 BL6 mice were divided into three groups; Castrated (CAS), Castrated with nandrolone decanoate (CAS+ND) and intact controls (CON). TA muscles were taken after 42 days of treatment for muscle wet weight analysis and AR quantification. Muscle weights were normalized to tibia length (mw/tl ± se). RESULTS: Castration decreased TA muscle weight 22% from the CON values, (2.5±.09mw/tl, 2.9±.17mw/tl), and CAS+ND (2.9±.1mw/tl) increased mass back to control levels. AR expression was decreased 36% in the CAS group when compared to the CON group. The CAS+ND group showed a five-fold induction in AR expression compared to CAS. CONCLUSIONS: Castration caused a reduction in TA mass, which is returned with steroid administration. In accordance with the muscle mass data, the AR expression is decreased with castration and increased with the addition of steroid. This data indicates there may be potential interaction between AR action and muscle mass regulation.