Correlation of mATPase, parvalbumin, and cytochrome c oxidase in rat skeletal muscle fibres.

Muscle fibre typing is conventionally performed on unfixed frozen sections. Within the particular classes of fibre types mATPase correlates well with the type of myosin heavy chain (MHC). However, investigation of other properties, e.g., parvalbumin (PV) level, cannot be determined on unfixed frozen sections. Determination of PV, which correlates with the relaxation time, is performed immunohistochemically on fixed tissue. By that method a comparison of mATPase activity and the amount of PV within the same muscle fibre is difficult. The present method, combining histochemistry of mATPase and cytochrome c oxidase with parvalbumin immunohistochemistry on consecutive sections, allows the distinction of six fibre types: I, IB, IIA, IIB, IIAB, IIX, and a C fibre population without division into IC and IIC fibres. The advantages and disadvantages of the present method are discussed.