HINDLIMB MUSCLE FIBER POPULATIONS OF FIVE MAMMALS

The fiber type profiles of hindlimb muscles in the Hartley guinea pig, Sprague-Dawley rat, cat, Galago senegalensis (lesser bushbaby) and Nycticebus coucang (slow loris) were estimated histochemically. Fibers were classified as fast oxidative glycolytic, fast glycolytic or slow oxidative according to their myosin adenosine triphosphatase, α-glycerophosphate dehydrogenase and reduced nicotinamide adenine dinucleotide diaphorase activities. It was found that the soleus and vastus intermedius muscles had the highest proportion of slow oxidative fibers in all five species, demonstrating the constancy of muscle fiber profiles dependent upon anatomical position and functional utilization. The tensor fascia latae and white vastus lateralis of the guinea pig were mostly fast glycolytic, while the red vastus lateralis of the guinea pig consisted of predominantly fast oxidative glycolytic fibers. The majority of muscles investigated in these five mammals were heterogeneous, having a wide range of percentages of the three fiber types.