Effects of testosterone suppression, hindlimb immobilization, and recovery on [H-3]ouabain binding site content and Na+, K+-ATPase isoforms in rat soleus muscle

摘要

We investigated the effects of testosterone suppression, hindlimb immobilization, and recovery on skeletal muscle Na+,K+-ATPase (NKA), measured via [H-3]ouabain binding site content (OB) and NKA isoform abundances (alpha(1-3), beta(1-2)). Male rats underwent castration or sham surgery plus 7 days of rest, 10 days of unilateral immobilization (cast), and 14 days of recovery, with soleus muscles obtained at each time from cast and noncast legs. Testosterone reduction did not modify OB or NKA isoforms in nonimmobilized control muscles. With sham surgery, OB was lower after immobilization in the cast leg than in both the noncast leg (-26%, P = 0.023) and the nonimmobilized control (-34%, P = 0.001), but OB subsequently recovered. With castration, OB was lower after immobilization in the cast leg than in the nonimmobilized control (-34%, P = 0.001), and remained depressed at recovery (-34%, P = 0.001). NKA isoforms did not differ after immobilization or recovery in the sham group. After castration, alpha(2) in the cast leg was similar to 60% lower than in the noncast leg (P = 0.004) and nonimmobilized control (P = 0.004) and after recovery remained lower than the nonimmobilized control (-42%, P = 0.039). After immobilization, beta(1) was lower in the cast than the noncast leg (-26%, P = 0.018), with beta(2) lower in the cast leg than in the noncast leg (-71%, P = 0.004) and nonimmobilized control (-65%, P = 0.012). No differences existed for alpha(1) or alpha(3). Thus, both OB and alpha(2) decreased after immobilization and recovery in the castration group, with alpha(2), beta(1), and beta(2) isoform abundances decreased with immobilization compared with the sham group. Therefore, testosterone suppression in rats impaired restoration of immobilization-induced lowered number of functional NKA and alpha(2) isoforms in soleus muscle.