The Influence of Characteristics of Actomyosin on the Difference of Rigor Mortis Progress between Cultured Red Sea Bream and Japanese Flounder

Abstract

As part of a study program to clarify the cause of differences in rigor mortis progress between cultured red sea bream and Japanese flounder, the superprecipitation reaction, the Mg²⁺-ATPase activity, and the Ca²⁺-sensitivity of actomyosin were measured at several Ca²⁺ and ATP concentrations, and these discrepant points were examined between both fishes. The superprecipitation reaction became higher with the increase of Ca²⁺ concentration from pCa 7.0 to pCa 5.0 and with the decrease of ATP concentration from 3.0mM to 0.5mM in both fishes, and the level was remarkably lower in cultured Japanese flounder than in cultured red sea bream. In both the Mg²⁺-ATPase activity and the Ca²⁺-sensitivity, similarly changing aspects were observed and these levels were also remarkably lower in cultured Japanese flounder than in cultured red sea bream. Although the significantly positive correlation was found between the superprecipitation reaction and the Mg²⁺-ATPase activity in both fishes, the distributive position of both values was clearly different between both fishes, and the superprecipitation reaction was higher in cultured Japanese flounder than in cultured red sea bream when the Mg²⁺-ATPase activity was the same level. This results suggest that the characteristics of actomyosin corresponding to muscular contraction might be remarkably different between both fishes and provide support to the difference of rigor mortis progress between both fishes.