抄録
Numerous subjective methods have been used for the classification of mammalian skeletal muscle fibre types. The value of SDH and myosin ATPase (mATPase) after acid preincubation for subdividing fast (type II) muscle fibre types in equine skeletal muscle, is assessed. Subjective visual assessment of the reaction intensity following SDH and mATPase after acid preincu bation is compared with microdensitometric measurements of the same muscle fibres. The relationship of SDH reaction product to mATPase reaction intensity is examined.
In the samples studied, visual assessment indicated that there appears to be two distinct reaction intensities for SDH. However, microdensitometry shows that the distribution of absorbances is over a continuous range of values with distinct peaks. The mATPase reaction after acid preincubation allowed visual discrimination of 4 reaction intensities, types I, IIab and IIa, in descending order of reaction intensity. However, microdensitometry showed a continuous range within the type II fibres with two or three overlapping peaks.
Plotting SDH absorbance versus mATPase absorbance showed that in some cases 4 clusters of fibres were present and that they compared well with the subjective classification by mATPase after acid preincubation. However, one case displayed only three clusters. The IIa and IIab groups overlapped.
These data are consistent with the hypothesis that IIab fibres are transitional between IIa and IIb.
