Chronic stimulation of rat skeletal muscle induces coordinate increases in mitochondrial and nuclear mRNAs of cytochrome-c-oxidase subunits.
Fast-twitch tibialis anterior muscle of the rat was subjected to chronic low-frequency (10 Hz, 10 h daily) nerve stimulation in order to investigate the time course of changes in cytochrome-c-oxidase activity, as well as in tissue levels of specific mitochondrially and nuclear-encoded, cytochrome-c-oxidase-subunit mRNAs. Chronic stimulation induced a progressive increase in cytochrome-c-oxidase activity which was threefold elevated after 35 days. A similar increase was recorded for citrate-synthase activity. Glyceraldehyde-3-phosphate dehydrogenase, which was studied as a glycolytic reference enzyme, moderately decreased, as did the tissue level of its corresponding mRNA. There was a parallel increase in the tissue levels of the two cytochrome-c-oxidase-subunit mRNAs over the entire stimulation time course. The extent of increase (stimulated/control) was 2.4 +/- 0.3 and 1.8 +/- 0.2 (means +/- SEM) for the mitochondrial and nuclear subunit mRNAs, respectively. This parallel increase suggested a coordinate regulation of the two subunits. The increase in cytochrome-c-oxidase activity initially corresponded to the changes at the mRNA level. However, with longer stimulation times (beyond 14 days), the increase in cytochrome-c-oxidase activity clearly exceeded that of the two mRNAs. This divergence was progressive and was interpreted to indicate that the increase in cytochrome-c-oxidase content was brought about not only by changes in the levels of the specific mRNAs, but also by alterations at the level of translation.
Hood
D A
DA
Fakultät für Biologie, Universität Konstanz, Federal Republic of Germany.
Zak
R
R
Pette
D
D
D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D015342:DNA Probes; D004558:Electric Stimulation; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism*; D004734:Energy Metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology*; D009132:Muscles / Q000201:enzymology* / Q000502:physiology; D009693:Nucleic Acid Hybridization; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D015342:DNA Probes; D012333:RNA, Messenger; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase