Submitted on September 15, 2006
Accepted on January 12, 2007
THE EFFECT OF EXTRACELLULAR OSMOLALITY ON CELL VOLUME
AND RESTING METABOLISM IN MAMMALIAN SKELETAL MUSCLE
AnaMaria Antolic1, Rosemarie Harrison1, Chris Farlinger1, Naomi M. Cermak1, Sandra J. Peters1, Paul LeBlanc1, and Brian D. Roy1*
1 Faculty of Applied Health Sciences, Brock University, St. Catharines, Canada
* To whom correspondence should be addressed. E-mail: brian.roy{at}brocku.ca.
The purpose of the current investigation was to establish an in-vitro mammalian skeletal muscle model to study acute alterations in resting skeletal muscle cell volume. Isolated, whole muscles (SOL and EDL) were dissected from Long Evans rats and incubated for 60 min in Sigma Medium-199 (1 g of resting tension, bubbled with 95:5% O2:CO2, 30 ± 2°C, and pH 7.4). Media osmolality was altered to simulate hypo-osmotic (190 ± 10 Osm; HYPO) or hyper-osmotic conditions (400 ± 10 Osm; HYPER), while an iso-osmotic condition (290 ± 10 Osm) served as a control (CON). Following incubation, relative water content of the muscle decreased with HYPER and increased with HYPO in both muscle types (p<0.05). The cross-sectional area of SOL type I and type II fibers increased (p<0.05) in HYPO while the HYPER exposure lead to no detectable changes. The EDL type II fiber area decreased in the HYPER and increased after HYPO exposure whereas no change was observed in EDL type I fibers. Furthermore, exposure to the HYPER 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 to CON and HYPO 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.
