Fig. 4

Heat shock protein 72 (HSP72) increases in flexor digitorum muscles of high repetition negligible force (HRNF) rats and co-localizes with osteoactivin (OA) in the sarcolemma. a ELISA of HSP72 protein levels in FRC and HRNF rat muscle lysates. Nanograms of protein were normalized to μg of total protein. b Representative Western blots of muscle homogenates probed with anti-HSP72 were used to confirm that the molecular weight of the HSP protein recognized by the antibody was the inducible form of HSP72. c Immunostained image of HSP72 (red) in muscle from a food restricted control (FRC) rat (a proximal portion of the muscle was resected and cut transaxially and shown), showing that there was little to no immunostaining. d Immunostained images of OA (green) in muscle from a FRC rat (a proximal portion of the muscle was resected and cut transaxially and shown) showing little to no immunostaining. e-g Double-labeled immunostained images of HSP72 (red) and OA (green) were merged in muscle images from an 8-week HRNF rat (a proximal portion of the muscle was cut transaxially and is shown). Arrows indicate HSP72 and OA co-localization in myofiber sarcolemma. The insets in e-g show enlarged regions of these images to illustrate co-localization of HSP72 and OA in myofiber sarcolemma. h Quantification of HSP72-positive immunostaining as a percent of total tissue area. *p < 0.05, compared to FRC rats. Scale bars in C-G = 50 μm