title: Relation between α-isoform and phosphatase activity of Na+,K+-ATPase in rat skeletal muscle fiber types.
abstract: In skeletal muscle the relationship between Na+,K+-ATPase activity and isoform content remains controversial (9,6). It could be due to the fiber-type content, membrane isolation and analytical methods. We investigated the distribution of subunit α1 and α2 Na+,K+-ATPase catalytic isoforms and the Na+,K+-ATPase activity in isolated membranes from white ( type I and glycolitic fibers) and red (type II and oxidative fibers) skeletal muscles. Red Gastrocnemius and White Gastrocnemius muscles were sampled from 8 week-old female Wistar rats and crude membranes were performed. The Na+,K+-ATPase activity and membrane distribution of Na+,K+-ATPase α1 and α2 isoforms were assessed by ouabain sensitive K-phosphatase (Kpase) measurements and Western Blot respectively. The Na+,K+-ATPase activity was 6 fold lower in White Gastrocnemius membranes than in Red Gastrocnemius membranes. The α1 and α2-isoform levels are higher in RG than in White Gastrocnemius. The α1 and α2-subunit Red Gastrocnemius content was significantly higher than in WG. The correlation between crude membrane Kpase activity and both catalytic α-subunit of the Na+,K+-ATPase exist.These data suggest that the Na+,K+-ATPase phosphatase activity correlates with the α1 and α2 isoforms levels in Red Gastrocnemius and White Gastrocnemius and confirms the fiber-specific Na+,K+-ATPase catalytic α-subunits and α2-isoform as the major catalytic isoform in rat skeletal muscle.
authors.affiliation: INSERM U927, School of Medicine, CHU/University Hospital, University of Poitiers, Poitiers, France.
authors.forename: M
authors.initials: M
authors.lastname: Chaillou
authors.forename: P
authors.initials: P
authors.lastname: Rigoard
authors.forename: M
authors.initials: M
authors.lastname: Fares
authors.forename: C
authors.initials: C
authors.lastname: Francois
authors.forename: Y
authors.initials: Y
authors.lastname: Sottejeau
authors.forename: J M
authors.initials: JM
authors.lastname: Maixent
mesh_terms: D000818:Animals; D005260:Female; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000166:cytology* / Q000201:enzymology*; D020033:Protein Isoforms / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D000254:Sodium-Potassium-Exchanging ATPase