Distribution of mitochondrial and lipidic alterations in abnormal extraocular muscle of rat.

An abnormal superior rectus muscle of rat displayed marked differences in the respective distributions of mitochondrial alterations and excessive lipid accumulations, both of which are thought to be indicators of faulty oxidative metabolism. The mitochondrial alterations were widespread, extending over 46% of muscle length. In contrast, the excess lipids extended over but 11% of the muscle length and were virtually confined to the end-plate region. The end plates themselves were essentially normal. These data raise the possibility that the end-plate region may exhibit a locally greater deficit of oxidative metabolism, due to a possibly higher metabolic requirement needed to support the localized end-plate potential activity.