Fig. 7.

Relative protein content. A: myosin regulatory light chain (RLC). B: troponin I (TnI). C: myosin binding protein C (MyBP-C). Proteins were identified with antibodies specific to either the slow or fast isoform of each protein. Protein content was normalized to total protein, expressed relative to the pooled homogenate control and then expressed relative to MHC content. Representative Western blots are shown for each protein along with the molecular weight marker from the corresponding Sypro Ruby-stained membrane. There were no age or sex differences except for TnI slow, where men had less content compared with women (P = 0.005). *Significant effect of sex. Significance level P < 0.05. Individual subjects are shown as symbols with group means indicated by gray horizontal lines. N = 6 subjects for each cohort except young men, where N = 5. C, control; L, ladder; OM, old men; OW, old women; YM, young men; YW, young women. Data were analyzed with a two-way ANOVA.