The Cytochemical Localization of Myoglobin in Striated Muscle of Man and Walrus

Myoglobin, the heme-protein responsible for the characteristic color of striated muscle (Kendrew, 1954), was the first protein to have its three-dimensional structure unravelled (Kendrew, 1961). However, virtually nothing is known concerning its localization within the muscle cell. Myoglobin oxidizes benzidine in the presence of of hydrogen peroxide. This reaction is well known and is used in the biochemical identification of myoglobin, but there have been few applications to the demonstration of the heme-protein in tissue sections. Drews and Engel (1961) first described peroxidatic activity in frozen sections of skeletal muscle and attributed it to myoglobin. Subsequently, Wachstein and Meisel (1964) suggested that this activity was associated with mitochondria and not myoglobin. The introduction by Karnovsky (1965) of a benzidine derivative, 3,3' diaminobenzidine (3,3' DAB) yielding a discrete, stable, and osmiophilic stain, rather than the microcrystalline product described in previous reports (Drews and Engel, 1961; Wachstein and Meisel, 1964), prompted this light and electron microscopic study of peroxidatic activity in striated muscle. The highest concentrations of myoglobin are found in the muscles of mammals that spend a great deal of time underwater. The muscle of whale and seal is reported to be almost black in