Abstract
The purpose of the present study was to investigate the structure of muscle mitochondria
for a possible early response to electrically induced short- and medium-term activity.
Rats were anesthetized with Na-pentobarbital. Both parts of the triceps surae muscle
were stimulated by direct electrical impulses for periods between 2 and 60 min. Biopsies
were taken and prepared for histological, enzyme-histochemical, and electron-microscopic
examinations. Enzyme histochemistry demonstrated an increase of oxidative activity
and an increase of RNA by NADH-tetra-zolium reductase and modified Gomori's trichrome
staining or acridine orange-induced fluorescence, respectively. These changes appeared
especially within type I fibers, as shown by ATPase reactions, and corresponded to
an increase in number and size of muscle mitochondria, followed by alterations of
the mitochondrial structure. The mitochondria reacted immediately to the electrical
stimulation of the muscle, and the degree of alteration depended on the duration of
the experiments.
These results suggest that mitochondria have a certain capacity for adapting rapidly
to changes in the energy metabolism. Beginning energetic decompensation may be responsible
for the alterations of the mitochondrial structure.
