A unique acid phosphatase location: the transverse tubule of avian fast muscle.

Acid phosphatase activity was localized cytochemically in the posterior latissimus dorsi muscle of the chicken. Reaction product was observed in three distinct structures: T-tubules, sarcoplasmic reticulum and dense bodies. Examination of cross- and longitudinal sections confirmed that the reaction product was membrane-limited. Acid phosphatase activity was observed in sarcoplasmic reticulum adjacent to the A-I junction and the A-band, in termyofibrillar dense bodies located along the length of the fibre and in the T-tubules but not in the surface caveolae or in the lateral sacs of the sarcoplasmic reticulum. The uniqueness of the T-tubular localization with respect to cytochemical localizations in other muscles is discussed.