Age-related differences in absolute numbers of skeletal muscle satellite cells.

The absolute number of satellite cells (SC) in young and adult rat skeletal muscle was estimated by correlating data from light and electron microscopic quantitation of myofiber nuclei (myonuclei and satellite cell nuclei) with biochemical assays for determining total muscle DNA content. Expressed both as a proportion of total myofiber nuclei and as absolute numbers, satellite cells are more numerous in the predominantly oxidative soleus muscle than in the mixed glycolytic/oxidative extensor digitorum longus (EDL) muscle at 1, 12, and 24 months of age. Satellite cell proportions decline gradually in both muscles with advancing age, but absolute numbers increase significantly in the soleus between 1 and 12 months, while EDL exhibits a continuous significant decline in satellite cells between each of the ages examined.