Effects of camptothecin, etoposide and Ca2+ on caspase-3 activity and myofibrillar disruption of chicken during postmortem ageing

Recently, a novel consideration has focused on the potential relationship of apoptosis and the protease caspases and the underlying mechanism for meat postmortem tenderization. In this study, apoptosis inducers, camptothecin and etoposide as well as Ca2+ were used to treat chicken muscle immediately after slaughter and follow the changes in caspase-3 activities and changes in the myofibrillar structures during 7 days of ageing. All three treatments resulted in significantly higher caspase-3 activities during storage (p < 0.05), with the natural substrates, whereas Western blotting analysis of the α-spectrin cleavage product, 120 kDa peptide (SBDP 120), showed that Ca2+ was more effective than either camptothecin or etopside, and all were most active up to day 3 (p < 0.01). According to SDS-PAGE, each treatment enhanced the accumulation of the 30 kD Troponin-T degradation product, especially during the first 3 days (p < 0.05), and this was supported by the degradation of myofibrils observed by electron microscopy (TEM). TEM images showed the treatments resulted in enlargement of the I-bands and shrinkage of A-bands; however Z-lines were only slightly affected, even at day 7. The findings revealed that the three apoptosis inducers could increase myofibrillar dissociation and proteolysis during the first 3 days of chicken meat ageing. Because of the high activity of caspase-3 during the early postmortem period, it is possible that caspase-3 contributes to the conversion of muscle into meat.