FISH MUSCLE CYTOSKELETON INTEGRITY IS NOT DEPENDENT ON INTACT THIN-FILAMENTS

Striated muscle cytoskeleton was studied by ultrastructure and electro phoresis. Treatment of sea bass white muscle myofibrils and glycerinat ed fibres with calpain caused disruption of costameres, intermediate f ilaments, and Z-line, without altering sarcomeres. V8 protease also ca used loss of costameres and Z-line, and disrupted sarcomeres without a ffecting the intermediate filaments. Recombinant lipase caused loss of Z-lines and also sarcolemma detachment, without changing sarcomeres o r intermediate filaments. DNase-1 removed thin filaments and partially removed Z-lines while leaving int-act the sarcolemma attachments and intermediate filaments. Calpain, V8 protease, lipase and DNase-1 treat ments induced extensive loss of alpha-actinin from the Z-line, which c ould be related to titin cleavage (calpain, V8), phosphoinositide hydr olysis (lipase), and actin depolymerisation (DNase-1). These results s how that the cytoskeletal components are independent of intact thin fi laments.