The histochemical profiles of fast fiber types IIB, IID, and IIA in skeletal muscles of mouse, rat, and rabbit.

This study characterized histochemically three fast fiber types (IIB, IID, IIA) in skeletal muscles of mouse, rat, and rabbit, with special reference to fiber types IIB and IID. The results are complemented by biochemical analyses of myosin heavy chain composition in these muscles. Fiber type delineation is based on various methods for mATPase staining with pre-incubations and assays under different conditions. In rat and mouse, IIB and IID fibers can be best distinguished according to their different mATPase stabilities towards formaldehyde and alkaline pH. In rabbit, the method of Matoba and Gollnick using acid pre-incubation provided best and most reproducible results. In addition to their different mATPase stabilities, the three fast fiber types differ with regard to their oxidative capacities and cross-sectional fiber areas in the three species. In general, Type IIB fibers are the largest and least oxidative, Type IIA fibers the smallest and most oxidative, and Type IID fibers intermediate. In rabbit...