Hydrostatic pressure studies of native and synthetic thick filaments: II. Native thick filaments from rabbit skeletal muscle.

Native thick filaments isolated from freshly prepared rabbit psoas muscle were found to be resistant to pressure-induced dissociation. With increasing pressure application and release, a bimodal distribution of filament lengths was observed. The shorter filament length is associated with filament breakage at the center of the bare zone, while the longer length is associated with relatively intact filaments. Intact filaments and filament halves decrease in length by no more than 20% after exposure to and release of 14,000 psi. Bimodal distributions were not observed in equivalent experiments performed on filaments isolated from muscle glycerinated and stored at -20 degrees C for 6 months. Instead, filament dissociation proceeds linearly as a function of increasing pressure. Filaments prepared from muscle glycerinated and stored for 2 and 4 months exhibited pressure-induced behavior intermediate between the filaments prepared from fresh muscle and filaments prepared from muscle stored for 6 months. Since there appears to be no difference in the protein profiles of the various muscle samples, it is possible that stabilization of the native thick filament against hydrostatic pressure arises from trapped ions that are leached out over time.