Figure 1.
Constitutively active PKB induces muscle fiber hypertrophy in regenerating (A–C) and adult (D–F) rat skeletal muscle. (A) Immunofluorescence analysis of a transverse section of regenerating denervated soleus muscle transfected with HA-tagged c.a. PKB and stained with anti-HA antibodies. Note that transfected fibers are much larger in size than surrounding untransfected fibers. (B) Serial sections of a regenerating denervated soleus muscle transfected with HA-tagged PKB and stained with antibodies specific for HA epitope (Upper) and MyHC-slow (Lower). Note that MyHC-slow is not expressed in the hypertrophic fiber expressing c.a. PKB. (C) Frequency histograms showing the distribution of cross-sectional areas (μm2) of fibers expressing c.a. PKB and surrounding untransfected fibers (control) in innervated (Left) and denervated (Right) regenerating soleus. A total of 1,920 muscle fibers were analyzed. (D and E) Denervated adult EDL (D) and soleus (E) muscles transfected with HA-tagged c.a. PKB. Hypertrophic fibers expressing c.a. PKB are seen in transverse sections stained with anti-HA. (F) Cross-sectional areas (μm2) of fibers expressing c.a. PKB and surrounding untransfected fibers (control) in innervated and denervated adult EDL and soleus muscles. Data are mean ± SEM. *, Significant difference from control group (P < 0.05). A total of 1,221 muscle fibers were analyzed. [Bars: 50 μm (A, B, and E); 100 μm (D).]