Slow/cardiac sarcoplasmic reticulum Ca2+-ATPase and phospholamban mRNAs are expressed in chronically stimulated rabbit fast-twitch muscle.
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.
Leberer
E
E
Banting and Best Department of Medical Research, Charles H. Best Institute, University of Toronto.
Härtner
K T
KT
Brandl
C J
CJ
Fujii
J
J
Tada
M
M
MacLennan
D H
DH
Pette
D
D
D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics*; D000252:Calcium-Transporting ATPases / Q000235:genetics*; D004558:Electric Stimulation; D015870:Gene Expression; D008297:Male; D009132:Muscles / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D012333:RNA, Messenger / Q000032:analysis*; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D000099211:Phospholamban
D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D012333:RNA, Messenger; D000099211:Phospholamban