Ultrastructural Evidence for Temperature-Dependent Ca2+ Release from Fish Sarcoplasmic Reticulum During Rigor Mortis

Abstract

The release or leakage of ca2+ from the sarcoplasmic reticulum (SR) during rigor mortis of fish muscle was investigated by transmission electron microscopy using pyroantimonate and related biochemical changes.\nCa2+ -pyroantimonate deposits were observed in the SR immediately after spiking the fish. At the onset of rigor for fish stored at 0°C, no deposits were found in the SR; however, fish stored for the same period at woe which were still in the pre-rigor state, clearly showed Ca2+ deposits in the SR.\nIn association with the Ca2+ translocation, ATP degraded faster at 0 c than at 10 °C, probably due to enhancement of myofibrillar ATPase activity by the increasing Ca2 + concentrations.\nTherefore, rapid Ca2+ release from the SR at 0°C seemed to trigger the acceleration of fish rigor mort is at this temperature, analogous to the phenomenon called "cold shortening."