Phagocytosis of the A band following Z line, and I band loss. Its significance in skeletal muscle breakdown.

A band phagocytosis, following Z line and I band loss, is described in polymyositis, in epsilon amino caproic acid induced myopathy and in an experimental myositis of guinea pigs. It is far less prominent in Duchenne muscular dystrophy. This form of necrosis is always associated with lesions in the plasma membrane. It is argued that the ensuing ionic equilibration with the extracellular fluid allows activation of a calcium activated proteinase (CAP) which digests the Z line. Breakdown of the myofibrils into individual A bands promotes rapid phagocytosis of the myofibre contents and facilitates regeneration of the muscle.