Muscle Growth-A Study on Fiber and Chemical Compositions

Abstract

Male Wistar rats having been sacrificed at 4th, 6th, 8th, 10th, 16th, and 26-38th weeks of age respectively, musculi rectus femoris were removed and subjected to histochemical and chemical analyses to investigate the growth of musculature. The examination at each age included five to eight animals. The analyses were made of the fiber area, fiber composition classified by the staining for myosin-ATPase and SDH, estimated total fiber number, and contents of water, protein, phospholipid, and triglyceride. The fiber areas at 4th week of age were 801, 539, and 619 μm^2 for the FG, FOG, and SO fibers respectively. The areas at 26-38th week of age were 6.1, 4.9, and 3.4 times greater for the FG, FOG, and SO fibers respectively than those at 4th week of age. As for the fiber composition, it was found that the aging after 6th week of age resulted in a decrease in the rate of FOC fiber and increase in FG fiber, whereas the rate of SO fiber was unchanged. The estimated total fiber number per muscle was decreased with aging. As for the chemical compositions, it was also found that the aging after 6th week of age caused a decrease in the phospholipid content, although the water and protein contents were unchanged. The triglyceride contents at 4th to 8th weeks of age were higher than those at 10th to 26-38th weeks of age. A possible explanation for these findings with aging was discussed.