Myosin isoform expression in skeletal muscles of turkeys at various ages.

The appearance of myosin isoforms in skeletal muscles of turkey embryos, poults, and toms was studied, using monoclonal antibodies raised against myosin isoforms in chicken fast-twitch muscle (Pectoralis). The myosin extract was prepared by repeated salt extraction-precipitation. The reactivity of monoclonal antibodies with turkey myosin isoforms was tested by an enzyme linked immunosorbent assay using alkaline phosphatase-conjugated antibody and detection by color development with p-nitrophenyl phosphate. Detection was also effected by protein slot blotting using peroxidase-conjugated antibody and color development with 3,3'-diaminobenzidine tetrahydrochloride. The monoclonal antibody AB8 was found to be specific for the adult myosin isoform, present in Pectoralis muscle of 14-day-old and adult turkeys and adult chickens. Subsequent peptide mapping also indicated that the adult myosin isoform of turkey Pectoralis muscle was nearly identical to the adult isoform from chickens. The monoclonal antibody 2E9 reacted with the myosin extract only from poults at ages of 7 days and 14 days posthatch, indicating that 2E9 is specific for the neonatal myosin isoform. The reactivity of 2E9 was noted with the muscle of the mixed fiber type (the thigh muscle group) as well as with the fast-twitch muscle (Pectoralis). Monoclonal antibodies EB 165 and AG6 were found to react with the myosin extract from all ages tested. Based on the reactivity with monoclonal antibodies, it was concluded that myosin in turkey muscles existed as at least three discrete isoforms that were expressed sequentially in the course of muscle development.