Nandrolone decanoate pre-treatment attenuates unweighting-induced functional changes in rat soleus muscle.

The effect of nandrolone decanoate pre-treatment (15 mg kg(-1) week(-1), for 6 weeks) was tested on the changes in mass and contractile properties of soleus muscle associated with 3 weeks of hindlimb suspension. Male rats were assigned to four groups (eight animals/group): control, nandrolone decanoate hindlimb-loaded, hindlimb-unweighted and nandrolone decanoate hindlimb-unweighted. Compared with age-matched control values, suspension induced a reduction in relative muscle mass and a shift in tension characteristics from slow-towards fast-twitch type. Nandrolone decanoate pre-treatment of suspended animals (nandrolone decanoate hindlimb-unweighted vs. nandrolone decanoate hindlimb-loaded) partially spared the relative soleus mass. Furthermore, (1) the relative twitch tension (nandrolone decanoate hindlimb-loaded: 5.4 +/- 0.7%; nandrolone decanoate hindlimb-unweighted: 5.1 +/- 0.5%), (2) the time to peak tension (nandrolone decanoate hindlimb-loaded: 152 +/- 9 ms; nandrolone decanoate hindlimb-unweighted: 167 +/- 15 ms), (3) the time constant of relaxation (nandrolone decanoate hindlimb-loaded: 274 +/- 12 ms; nandrolone decanoate hindlimb-unweighted: 245 +/- 20 ms), (4) the relative K+ contracture tension (nandrolone decanoate hindlimb-loaded: 81.7 +/- 3.8%; nandrolone decanoate hindlimb-unweighted: 86.9 +/- 4.2%) and (5) the relative caffeine contracture tension (0.5 mM) (nandrolone decanoate hindlimb-loaded: 5.2 +/- 0.8%; nandrolone decanoate hindlimb-unweighted: 5.9 +/- 1.1%) were not significantly modified. The present results demonstrate that exogenously provided nandrolone decanoate pre-treatment attenuates functional changes occurring in soleus muscle subject to unweighting.