Effects of high pressure treatment on Mg-enhanced ATPase activity of rabbit myofibrils

Effects of high pressure treatment on the Mg-enhanced ATPase activity of myofibrils were studied to investigate the pressure-induced modification of actin-myosin interaction. In the myofibrils prepared from muscles, similarities in the changes in the Mg-enhanced ATPase activity and its sensitivity to ionic strength were observed between muscles pressurized up to 200 MPa and muscles conditioned for 7 days. The BIMA (Biological Index of Myofibrillar Ageing) value of the pressurized myofibrils reached the same level as that of the conditioned myofibrils. When the isolated myofibrils were pressurized, slight increases of ATPase activity below 0.2 m KCI and of BIMA value were observed in the myofibrils pressurized at 30 MPa, which then decreased with increasing pressure. The release of soluble materials from the myofibrils was markedly accelerated by pressurization above 150 MPa. The SDS-PAGE analysis showed that the release of the constituents of thin filaments seemed to proceed prior to the release of the constituents of thick filaments. The pressure-induced changes in Mg-ATPase activity and BIMA value are explained in terms of the structural change of thin filaments resulting from briefly exposing muscles to high pressure.