Temperature acclimation has no effect on ryanodine receptor expression or subcellular localization in rainbow trout heart
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In cardiomyocytes, ryanodine receptors (RYRs) mediate Ca2+-induced Ca2+-release (CICR) from the sarcoplasmic reticulum (SR) during excitation–contraction (e–c) coupling. In rainbow trout heart, the relative importance of CICR increases with cold-acclimation. Thus, the aim of this study was to investigate the effect of temperature acclimation (4, 11 and 18°C) on RYR intracellular localization and expression density. We used immunocytochemistry to assess intracellular localization in ventricular myocytes and Western blotting to assess RYR expression in both atrial and ventricular tissue. In ventricular myocytes, RYRs were localized peripherally in transverse bands aligning with sarcomeric m-lines and centrally around mitochondria and the nucleus. Localization did not change with temperature acclimation. RYR expression was also unaffected by temperature acclimation. The localization of RYRs at the m-line is similar to neonatal mammalian cardiomyocytes. We suggest this positioning is indicative of myocytes which rely predominantly on transsarcolemmal Ca2+-influx, rather than CICR, during e–c coupling.
KeywordsOncorhynchus mykiss Excitation–contraction coupling Sarcoplasmic reticulum Immunocytochemistry Ryanodine receptor CICR
- INCX rev
Reverse-mode NCX current
Sodium dodecyl sulphate
Tween tris-buffered saline
The authors thank Peter March and Jane Kott for their assistance with the microscopy and Dr Andy Trafford for supplying the rat heart samples. We are very grateful to Dr A. Chugun and Dr. T. Murayama for providing the antibody against RYR. This study was funded by the BBSRC and The Danish Natural Science Research Council.
- Sephton DH, Driedzic WR (1995) Low temperature acclimation decreases the rate of protein synthesis in rainbow trout (Oncorhynchus mykiss) heart Fish. Physiol Biochem 14:63–69Google Scholar