Histochemical staining patterns of muscle fibres in the gastrocnemius, soleus and anterior tibial muscles of the adult cat, as viewed in serial sections stained for lipids and succinic dehydrogenase.

Abstract

The histochemical staining patterns of fibres in the gastrocnemius, soleus and anterior tibial muscles of the adult cat were investigated in serial sections stained for lipids, succinic dehydrogenase and NADH2 tetrazolium reductase. In the gastrocnemius and anterior tibial muscles, fibres of four different staining patterns were described, three of which were regarded as corresponding to those of the FF, FR and S fibres defined in the cat by Burke et al. (1973). The fourth fibre type, which was not always recognized, showed a spectrum of staining properties intermediate between those of the presumed FF and FR fibres. In the soleus muscle the majority of fibres exhibited an appearance which was similar but not identical to that of the S fibres of the composite muscles. A small percentage of the soleus fibres showed atypical staining properties and were believed to correspond to the fast contracting units observed in this muscle (Hammarberg & Kellerth, in preparation). For all three muscles the relative proportion of different types of muscle fibres were calculated, as well as the distribution of fibre diameters within each type.