Figure 1.
Skeletal muscle protein synthesis is impaired in tumor-bearing mice, whereas fiber type composition is unchanged. Male and female 7-week–old mice were injected with LLC1 tumor cells or vehicle control (PBS). A, 21 days post-injection, the FSR of mixed muscle protein and of proteins in myofibrillar, sarcoplasmic, and mitochondrial muscle fractions were measured by in vivo stable isotope labeling and subsequent MS analysis of isotope incorporation into protein. B and C, muscle fiber type composition was assessed by immunohistochemical staining of laminin (blue staining, indicated by blue arrow) to define the fiber sarcolemma, MyHCslow (green) to identify Type I fibers, and MyHCIIA (red) to identify type IIa fibers. Fibers without staining were classified as Type IIx and/or IIb fibers (labeled in white). *, signifies significant differences (p < 0.05) between PBS-injected and LLC1-injected tumor-bearing mice. Data are presented as mean ± S.D.