title: Effect of extracellular osmolality on cell volume and resting metabolism in mammalian skeletal muscle.
abstract: The purpose of the present investigation was to establish an in vitro mammalian skeletal muscle model to study acute alterations in resting skeletal muscle cell volume. Isolated, whole muscles [soleus and extensor digitorum longus (EDL)] were dissected from Long-Evans rats and incubated for 60 min in Sigma medium 199 (1 g of resting tension, bubbled with 95% O(2)-5% O(2), 30 +/- 2 degrees C, and pH 7.4). Medium osmolality was altered to simulate hyposmotic (190 +/- 10 mmol/kg) or hyperosmotic conditions (400 +/- 10 mmol/kg), whereas an isosmotic condition (290 +/- 10 mmol/kg) served as a control. After incubation, relative water content of the muscle decreased with hyperosmotic and increased with hyposmotic condition in both muscle types (P < 0.05). The cross-sectional area of soleus type I and type II fibers increased (P < 0.05) in hyposmotic, whereas hyperosmotic exposure led to no detectable changes. The EDL type II fiber area decreased in the hyperosmotic condition and increased after hyposmotic exposure, whereas no change was observed in EDL type I fibers. Furthermore, exposure to the hyperosmotic condition in both muscle types resulted in decreased muscle ATP and phosphocreatine (P < 0.05) contents and increased creatine and lactate contents (P < 0.05) compared with control and hyposmotic conditions. This isolated skeletal muscle model proved viable and demonstrated that altering extracellular osmolality could cause acute alterations in muscle water content and resting muscle metabolism.
authors.affiliation: Faculty of Applied Health Sciences, Brock Univ, St Catharines, ON, Canada.
authors.forename: AnaMaria
authors.initials: A
authors.lastname: Antolic
authors.forename: Rosemarie
authors.initials: R
authors.lastname: Harrison
authors.forename: Chris
authors.initials: C
authors.lastname: Farlinger
authors.forename: Naomi M
authors.initials: NM
authors.lastname: Cermak
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Peters
authors.forename: Paul
authors.initials: P
authors.lastname: LeBlanc
authors.forename: Brian D
authors.initials: BD
authors.lastname: Roy
mesh_terms: D000818:Animals; D001481:Basal Metabolism / Q000502:physiology*; D048429:Cell Size; D045604:Extracellular Fluid / Q000737:chemistry* / Q000502:physiology*; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000166:cytology* / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D009994:Osmolar Concentration; D051381:Rats; D020318:Rats, Long-Evans; D012146:Rest / Q000502:physiology; D014867:Water / Q000502:physiology
chemical_list: D014867:Water