Post-mortem extension of ovine longissimus muscle influences the degradation of titin and calpain 3 : A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science with Honours at Lincoln University

Two hanging methods were compared for the ageing of lamb carcasses. Hanging the carcasses over a bar in a bent conformation (bar-hung) resulted in greater extension of the longissimus thoracis et lumborum (LTL) than in carcasses hung conventionally by the Achilles tendons. The sarcomeres were approximately two-thirds longer in bar-hung carcasses. The bar-hanging caused a slight increase in the rate of production of an undefined fragment of titin (connectin) as determined by SDS-polyacrylamide gel electrophoresis. This was most apparent 2 days post-mortem and could be due to conformational change of titin molecules caused by extension of the LTL. Western blotting was used to show that bar-hanging also caused an increase in the rate of calpain 3 (p94) degradation. These results support the hypothesis that the activity of calpain 3 is influenced by the degree of muscle extension. This calpain 3 response could rely on interaction with titin, and thereby form a mechanism by which skeletal muscle can respond to strain, but further research is required to verify this possibility