Journal of Dental Research, Vol 77, 1926-1930, Copyright © 1998 by International & American Associations for Dental Research Online Journals
Developmental changes in enzyme activities and in structural features of rat masticatory muscle mitochondria
I. Sato, K. Konishi, T. Kuramochi and T. Sato
Department of Anatomy, School of Dentistry at Tokyo, Nippon Dental University, Japan.
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-O2 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 postnatal rat. However, a notable increase was found in
the cross-sectional area of mitochondria between 10 and 15 days
postnatally. The number of mitochondria per muscle fiber was apparently
constant during the same period. We demonstrated that the change in feeding
behavior was well-correlated with an increase in mitochondrial enzyme
activity, also supported by the early structural development of
mitochondria.
