Developmental Changes in Enzyme Activities and in Structural Features of Rat Masticatory Muscle Mitochondria

The functional ability of a muscle is closely related to the activities of the mitochondria, which are energy-producing organelles in muscle cells. The development of the mammalian masticatory muscle progresses dramatically when feeding behavior changes from suckling to mastication, but it is unclear how the energy-producing systems of the mitochondria change. In this paper, the development of rat masticatory muscle mitochondria was investigated in terms of enzyme activities of the mitochondrial respiratory chain and the structural and numerical development of mitochondria, especially regarding the change in feeding behavior from suckling to mastication. Using isolated mitochondria from the masticatory muscle, we measured succinate dehydrogenase, NADH dehydrogenase, succinate-O2 oxidoreductase, and NADH-O 2 oxidoreductase. These were found to be increased in the 15-day postnatal rat compared with the 0-to 10-day postnatal rat. The structural development of mitochondria was gradual in the 0- to 15-day post...