Light and electron microscopic studies on localization of myoglobin in skeletal muscle cells in neuromuscular diseases

The localizations of myoglobin in skeletal muscle cells of patients with Duchenne muscular dystrophy (DMD), myotonic dystrophy (MyD), and amyotrophic lateral sclerosis (ALS) were studied by immunohistochemistry and immunoelectron microscopy. In normal skeletal muscle cells, myoglobin was localized mainly in the I-band region. In degenerating muscle cells of patients with DMD and MyD, myoglobin was also demonstrated in the distended lumen of the internal membrane system and in the intermyofibrillar space, through which it seemed to pass into the extracellular space. No myoglobin was detected in opaque fibers or in some of small-sized fibers in DMD muscle. In patients with ALS the staining intensities of myoglobin varied in different muscle cells, but myoglobin was restricted to the I-band region in many muscle cells. These findings suggest that changes in the localization of myoglobin in skeletal muscle cell sensitively reflect the pathologic status of muscle cells.