Morphometric analysis of satellite cells in rat skeletal muscles: soleus and extensor digitorum longus.

Satellite cells (SC) are present in all types of skeletal muscles. They can exhibit DNA replication and mitotic divisions throughout their life. Depending on the kind of muscle, a different number of SC is present. The aim of this study was to establish whether the differences in muscle metabolism are reflected in the quantitative ultrastructural evaluation of their SC. Two skeletal muscles of rats, soleus (SOL) with predominant slow fibers and extensor digitorum longus (EDL) with predominant fast ones, were studied. Morphometric analysis was performed according to the modified method of Weibel [Stereological Methods, vol 1: Practical Methods for Biological Morphometry. London, Academic Press, 1979]. In the SC of EDL mitochondria, rough endoplasmic reticulum and Golgi apparatus were less frequent as compared with the SOL. The volume fractions of these organelles were much higher in SC of SOL than in EDL. The ribosomes and polyribosomes were more densely packed in SC of SOL than in EDL. Ultrastructural morphometric evaluation demonstrated significant differences between the SC components of two different muscles: a slow (SOL) and a fast (EDL) one.