Ultrastructural changes and glutathione level were investigated in the pectoralis muscle of rats fed a low-protein diet. Electron microscopy demonstrated the ultrastructural changes of occasional myofibrils affected with protein deficiency that were characterized with the streaming and/or disruption of the Z-line and disintegration of sarcomeric striation, In the affected sarcomeres, sarcomere length was often elongated and fragmented thick filaments were present together with dense amorphous materials flowing from the damaged Z-line. Glutathione level of muscle in the low-protein diet group (5% casein) was reduced to about one-third of that in the control diet group (20% casein), The study suggests that depletion of glutathione by protein malnutrition is responsible for inducing myofibrillar damage through the excess leaking of Ca2+ into the cytosol.
