Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

The sarcoplasmic/endoplasmic reticulum Ca2+-ATPases (SERCAs) change in a quite predictable pattern in regenerating and stretched rat muscles. Our study extended mostly to the mRNA isoforms but the levels of the muscle specific SERCA proteins were also followed. The extensive muscle necrosis, induced by the intramascular injection of the notexin containing venom of the Australian tiger snake, abolishes all SERCA isoforms. The muscle regenerates itself in four weeks. During regeneration of fast (EDL) and slow (soleus) muscles the neonatal isoform SERCA1b appears first and later it is gradually replaced by the adult fast isoform SERCA1a. In slow muscle the fast adult isoform is dominant until the time of innervation, then the level of slow isoform starts to increase. Changes of the protein levels followed the mRNA levels, and by the end of regeneration the muscles contained a similar ratio of SERCA isoforms as their lateral counterparts. In the muscle fibers the expression of the sarcoplasmic reticulum Ca2+-ATPases show dramatic differences between normal and regenerated muscles. After regeneration in the soleus muscle 98% of the fibers express the slow muscle specific SERCA2a isoforms (these are real slow fibers, also expressing the slow myosin heavy chain isoform). However such fibers are only 81% of total in the normal soleus muscle. The regeneration also increased the number of hybrid fibers (expressing both fast and slow SERCA isoforms). This change in the fast-twitch EDL muscle coincides with the more frequent grouping of slow SERCA-expressing fibers compared to the normal muscles. In soleus muscles immobilized for three days in an extended position the mRNA level of SERCA1b isoform increases and the SERCA1a decreases. These changes are similar to that observed at the beginning of regeneration.

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Poster Number PAzador0699
Keywords: serca, muscle, regeneration, stretch, adaptation