Studies on Fish Sarcoplasmic Reticulum

点击翻译按钮获取中文摘要

Sarcoplasmic reticulum (SR) is an organ which controls muscle intracellular Ca^<2+> concentration and found in fish muscle. This study deals with characterization of SR from a few fishes and its possible role in rigor mortis progress.1. Spiked plaice was stored at 0 or 10ﾟC and examined for changes in Ca^<2+> concentration in the ordinary muscle SR by electron microscopic observation. Ca^<2+> in SR disappeared faster at 0ﾟC than at 10ﾟC with a faster development in rigor tension at 0ﾟC. In addition, fragmented SR prepared from plaice showed the lowest Ca^<2+> uptake when measured at 0ﾟC.2. Plaice myofibrillar Mg^<2+>-ATPase activity was lower at a reaction temperature of 0ﾟC than at 10ﾟC in the absence of Ca^<2+>, the condition corresponding to a relaxed state of muscle. Since the previous results suggest that intracellular Ca^<2+> concentration increases quickly when plaice is stored at 0ﾟC, myofibrillar Mg^<2+>-ATPase activity was measured at this temperature in the presence of Ca^<2+>. The activity was higher than that at 10ﾟC in the absence of Ca^<2+>.3. Fragmented SR from carp ordinary muscle was further purified into heavy and light SR fractions. HSR fraction contained many round vesicles, some of them with feet structures on the surface. SDS-gel electrophoresis revealed that carp SR was composed mainly of Ca^<2+> pump protein with a subunit molecular weight of 95,000 (95kDa) and of 70kDa, 35kDa and 10kDa Ca^<2+>-binding proteins.4. Carp acclimated to 30ﾟC was faster in rigor mortis progress than that acclimated to 10ﾟC when stored at 0ﾟC after spiking. Correspondingly, Ca^<2+> uptake by SR from warm-acclimated carp was lower at a reaction temperature of 0ﾟC than that from cold-acclimated carp.5. The above results suggest that fish SR plays an important role in rigor mortis in terms of affecting intracellular Ca^<2+> concentration after death.