Immunohistochemical and ultrastructural distribution of antibodies to troponin-C and troponin-I in normal and dystrophic chicken skeletal muscle.

The pectoral muscles from normal and dystrophic chickens were reacted with rabbit antisera to troponin-C and to troponin-I, and the distribution of antibodies was determined by fluorescence microscopy of antibody-stained myofibrils and immuno-electron microscopy of separated I band segments. Chickens of dystrophic strain 308 and control New Hampshire hens were used in this work. Myofibrils which were prepared from both normal and dystrophic muscles and reacted with anti-troponin-I were fluorescent in the I band and A band regions. The Z lines and H zones were unstained. Myofibrils prepared from normal pectoral muscle and treated with anti-troponin-C yielded a pattern of fluorescence similar to that for anti-troponin-I treated myofibrils. However, those myofibrils isolated from dystrophic muscle and reacted with anti-tropinin-C had a weak fluorescence over their entire lengths, and discrete A- and I-band staining was not visible. These results were confirmed by ultrastructural studies of separated I segments reacted with the antisera. It is concluded that in the dystrophic muscle either the antigenic sites of troponin-C are changed which results in a loss of antibody-combining ability or these sites are masked in some way which prevents the reaction with the antibody.