抄録
Remarkable differences between rigor mortis and thaw rigor were examined in the muscle of carp. Glycolysis seems to be one factor which influences the amount of ATP. In the muscle of carp stored at 18℃ after instant death, the extent of rigor mortis was small, and the amounts of glycogen and ATP gradually decreased, while that of lactate increased slowly. On the other hand, the muscle of carp frozen rapidly after instant death and subsequently thawed and stored at 18℃ showed strong thaw rigor. Glycogen and ATP amounts decreased remarkably by the end of thaw rigor, whereas that of lactate increased markedly in thaw rigor. In the case of thaw rigor, it can be concluded that the contraction energy is mainly due to the large amount of ATP supplied through the rapid glycoysis. Influences of storage temperatures on the prolongation of pre-rigor period of sea bream were examined. The amount of ATP in the muscle of sea bream decreased more rapidly and rigor mortis proceeded faster at 0℃ than at 10℃. In the muscle stored at 10℃ the onset of rigor mortis occurred seven hours later than at 0℃. Wild and cultured of sea bream were stored at 0℃ and 10℃, and compared to each other with respect to the progress of rigor mortis. Rigor mortis began to occur earliest in the cultured specimen stored at 0℃, followed successively by the wild one at 0℃, the cultured one at 10℃, and the wild one at 10℃, demonstrating that the pre-rigor period of sea bream can be most effectively attained in the last case. The mechanism of thaw rigor was investigated in carp muscle in relation to myofibrillar ATPase and sarcoplasmic reticulum (SR) Ca^<2+> uptake activities as well as the change in muscle ultrastructures. No significant difference between carp immediately after death and that in thaw rigor was observed in myofibrillar ATPase. Ca^<2+> uptake activity of SR from the sample immediately after death was high, but it was nearly zero during thawing. Electron microscopic observation revealed that SR membranes were broken by freezing and thawing. The resultant Ca^<2+> release from SR probably caused the increase of ATP consumption and the acceleration of thaw rigor by activating myofibrillar Mg^<2+>-ATPase.
