CALCIUM-CHLORIDE IN-VITRO EFFECTS ON ISOLATED MYOFIBRILLAR PROTEINS

The objective of this study was to determine the effect of 30 mm CaCl2 on the solubilization of those structural proteins that contribute to myofibril stability. Ovine M. longissimus dorsi (longissimus) samples were obtained immediately post-exsanguination, myofibrils were isolat ed, glycerated, and frozen until needed. Myofibrils were washed, dilut ed and incubated in 0.1 m KCl, 10 mm Tris, pH 7.0 buffer for 24, 48 an d 72 h. Treatments consisted of: (1) control, (2) mm E64, (3) 30 mm Ca Cl2, and (4) mm E64 + 30 mm CaCl2. Results (SDS-PAGE) indicated that m yosin heavy chain (though not to a great extent), M-protein, C-protein , alpha-actinin, actin, troponin-T, tropomyosin isoforms, troponin-I a nd 72, 70, 62, 33, 32, 30, and 22 kDa unidentified bands were solubili zed from myofibrils incubated in KCl buffer for 72 h. The addition of CaCl2 hastened the appearance of some of the proteins in the supernata nt fractions, but no differences were observed at 72 h among the treat ments. The addition of E64 had no effect on which proteins were releas ed. Thus, in the absence of proteolysis it appears that a general solu bilization of thick-and-thin filament ancillary proteins occurs in the presence of 30 mm CaCl2. However, the contribution to tenderness shou ld be minimal, because solubilized proteins are not part of the cytosk eletal elements that are responsible for maintaining structural integr ity of the tissue.