A Histochemical Method for the Simultaneous Demonstration of Capillaries and Fiber Type in Skeletal Muscle

A modified ATPasc method for the simultaneous demonstration of capillaries and fiber types in skeletal muscle is presented. Muscle biopsies were obtained front mice, hamsters, rats, cats, and dogs, quick frozen, and sectioned at 8 μm in a cryostat. The frozen slides were fixed in a neutral formalin solution at 4 C for 5 min, and then incubated at 37 C for 1 hr in a medium containing ATP, Pb²⁺, and Ca²⁺ in a tris-maleate buffer (pH 7.2). Dilute (NH₄)₂S was used as a developer. To test the reliability of the proposed method, serial sections of each biopsy were stained separately for capillaries (amylase-PAS method) and for fiber types by a standard myosin ATPase (m-ATPase) method. Fiber type percent and capillary parameters were determined for each biopsy. No difference in results was observed for parameters determined using the modified ATPase method compared to the standard capillary and fiber type staining methods. This modified technique is therefore suitable for the simultaneous demonstration of capillaries and fiber types in skeletal muscle.