EASILY RELEASABLE MYOFILAMENTS IN POSTMORTEM BOVINE MUSCLE

Easily releasable myofilaments (ERM) were prepared from bovine sternom andibularis muscle myofibrils at 0 time and after intervals of 1 day, 7 and 14 days post mortem ageing at 2-degrees-C. ERM were released fro m myofibrils by gentle agitation in a relaxing solution containing 2mM Mg++-ATP and 2 mM 1,2-bis(2-dicarboxymethylaminoethoxy)ethane (EGTA). Myofilaments were also released in the absence of ATP (controls). ERM yields (% of total myofibrillar protein) rose gradually from 1.40% at 0 time to 5.50% at 14 days (P<0.001). Control yields rose from 0.33% at 0 time to 1.16% after 14 days (P<0.05). Examination of ERM in the t ransmission electron microscope showed separated thick and thin myofil aments. No other structures were seen. Myofilament lengths changed lit tle over the ageing period but the ratio of thin to thick myofilaments increased. Subunit composition of ERM, as assessed by SDS-PAGE, was s imilar to previous reports for other species.