RAT SKELETAL MUSCLE RHOA EXPRESSION WITH FUNCTIONAL OVERLOAD AND ANABOLIC STEROID ADMINISTRATION.

Abstract

RhoA exerts signaling involved in the formation of focal adhesion complexes and is a potentially important mediator of muscle gene regulation during overload induced growth. PURPOSE: To determine what effect functional overload with and without nandrolone decanoate (ND) administration had on RhoA expression in rat plantaris muscle. METHODS: Male Sprague Dawley (125g) rats were randomly assigned to Con (n = 9), 3 day (n = 5), or 21 day (n = 5) overload groups. Compensatory overload (OV) was induced by the synergist ablation of the distal 1/3rd of the medial and lateral gastrocnemius muscles of the hindlimb. Animals were randomly assigned to intramuscular injections of Sesame Oil (n = 12) or ND (n = 12, 6mg/kg). At the appropriate time animals were anesthetized and the fast twitch plantaris muscle was excised and frozen for analysis of muscle mass, protein concentration, RNA concentration, and RhoA expression. RESULTS: Muscle mass (mg) significantly increased (p < 0.05) from Con (109 ± 4) with 3 days of OV (143 ± 3) and OV+ND (144 ± 4) administration. Muscle mass also significantly (p < 0.05) increased from Con (257 ± 7) with 21 days of OV (309 ± 3) and OV+ND (333 ± 5) administration. RNA concentration (ug/mg) increased (p < 0.05) from Con (1.77 ± .1) with 3 days of OV (2.64 ± .44) and OV+ND (2.57 ± .12). Similarly with 21 days of OV+ND, RNA concentration increased (1.68 ± .16) from Con (1.19 ± .13). Western Blot analysis revealed an increase (p < 0.05) in RhoA expression at 3 days from Con (1.06 ± .13) with OV (2.15 ± .21), ND (1.76 ± .11) and OV+ND (3.85 ± .62). RhoA expression remained elevated from Con (1.00 ± .34) at 21 days with ND (3.80 ± .35). CONCLUSION: RhoA expression is induced by OV and ND administration alone. However, there is a synergistic effect of OV+ND to increase RhoA expression in rat plantaris muscle. The results of this study suggest that increases in RhoA expression with OV and/or OV+ND mirror increases in mass in the fast twitch plantaris muscle of adult rats. Supported by the South Carolina Space Grant Consortium and American College of Sports Medicine NASA Space Grant.