Temperature‐Dependency of Rigor‐Mortis of Fish Muscle: Myofibrillar Mg ²⁺ ‐ATPase Activity and Ca ²⁺ Uptake by Sarcoplasmic Reticulum

Abstract

ABSTRACT Myofibrillar Mg 2+ ‐ATPase activity of plaice and red sea bream increased with increase in reaction temperature and Ca 2+ concentration. However, temperature decrease tended to lower Ca 2+ sensitivity of Mg 2+ ‐ATPase activity. While it was assumed that spiked fish muscle was relaxed and the myofibrillar Ca 2+ concentration was low, the progress rate of rigor‐mortis correlated well with Mg 2+ ‐ATPase activity in the presence of a few micromolar Ca 2+ at 0°C. Correspondingly, it was found that Ca 2+ uptake by plaice sarcoplasmic reticulum decreased with the decrease in reaction temperature. These results strongly suggest the acceleration of fish rigor‐mortis at 0°C is due to the increase of Ca 2+ concentration in myofibrils during storage at this temperature.