DISTRIBUTION AND RELATIVE SIZES OF 3 HISTOCHEMICAL FIBER TYPES IN RAT TIBIALIS ANTERIOR MUSCLE

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 123  (FEB) , 1-19
Abstract
A quantitative study of the tibialis anterior muscle of the adult rat showed that the proportion of each histochemical fiber type varied between adjacent regions along the deep to superficial and medial to lateral axes of the muscle. The distribution of fiber types classified with oxidative enzymes was similar to that using phosphorylase, but differed from that obtained with sections stained for myosin ATPase. This apparent discrepancy in classification was confirmed by comparison of the relative ranges of fiber cross sectional areas for fiber types classified on the basis of their oxidative enzyme and ATPase activities and by an independent analysis of individual fibers in serial sections stained for succinic dehydrogenase and myosin ATPase (pH 9.4, using formalin fixed, alkaline preincubated material). Some fibers classified as Type 1 on the basis of their level of staining with ATPase, could also be classified as Type 11A when identified in section exhibiting succinic dehydrogenase activity. Fibers classified as Type 1 using the latter enzyme technique were divided into 2 subclasses with ATPase. While some fibers showed the low level of ATPase activity normally associated with the Type 1 fiber class, others possessed the higher activity and typical floccular appearance of Type 11A fibers.