Flexor digitorum tendons show increased osteoactivin (OA) and heat shock protein 72 (HSP72) by six weeks of high repetition negligible force (HRNF) task performance. a Representative Western blot of tendon homogenates probed with anti-OA. Band detected is the 47 kDa MW. β-actin was used as a loading control (at 42 kDa). b Densitometric analysis of the 47 kDA OA band in tendon from three replicate Western blots after normalization to β-actin levels. c-f Immunostaining and quantification of OA in food restricted control (FRC) and HRNF rat tendons (T). A tendon region located proximal to the wrist and cryosectioned longitudinally, is shown. Arrows indicate representative OA-immunopositive cells, many of which are tenocyte-like in appearance. Fibroblast-like cells were also observed in the epitendon (one indicated with an asterisk in panel E and enlarged in the inset) as well as macrophage-like cells (arrow heads). g-i Immunostaining and quantification of HSP72 in FRC and HRNF rat tendons (T). Arrows indicate representative HSP72-immunopositive cells that appear tenocyte-like. *p < 0.05, **p < 0.01, compared to FRC rats. Scale bars in D-F,H = 50 μm; Scale bar in G = 100 μm. n.s. = not significant.