Cytochemical observations of two distinct acid phosphatase-reactive structures in anterior latissimus dorsi muscle of the chicken

Acid phosphatase activity has been localized cytochemically in the avian anterior latissimus dorsi muscle in two distinct structures, the sarcoplasmic reticulum and membrane-limited dense bodies. Cross and longitudinal sections confirmed that the reaction product was membrane-bound. Acid phosphatase activity was observed in the longitudinal tubules of the sarcoplasmic reticulum in the region of the I band and in dense bodies located along the length of the fibre just beneath the sarcolemma and between the myofibrils. This dual localization is discussed in relationship to previous cytochemical and zonal centrifugation evidence for more than one acid phosphatase-containing organelle in skeletal muscle.