Slow/cardiac sarcoplasmic reticulum Ca2+-ATPase and phospholamban mRNAs are expressed in chronically stimulated rabbit fast-twitch muscle |
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Authors: | E Leberer K T H?rtner C J Brandl J Fujii M Tada D H MacLennan D Pette |
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Institution: | Banting and Best Department of Medical Research, Charles H. Best Institute, University of Toronto. |
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Abstract: | Fast-twitch extensor digitorum longus muscles of the rabbit were subjected to chronic low-frequency stimulation during different time periods. Changes in the relative amounts of mRNAs encoding fast and slow/cardiac Ca2+-ATPase isoforms were assessed through the use of an RNase-protection assay. Stimulation-induced increases in slow cardiac Ca2+-ATPase and phospholamban mRNAs were quantified by mRNA hybridization. Prolonged stimulation resulted in an exchange of the fast with the slow/cardiac Ca2+-ATPase isoform mRNAs. The exchange was complete after 72 d of stimulation as compared with normal slow-twitch soleus muscle. The tissue content of phospholamban mRNA reached levels similar to that found in normal slow-twitch soleus muscle by the same time. The conversion of the sarcoplasmic reticulum coincided with the fast-to-slow troponin C isoform transition, previously investigated in the same muscles. |
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