Abstract:
The purpose of the current investigation was to establish an in-l'itro skeletal
muscle model to study acute alterations in resting skeletal muscle cell volume. Isolated.
whole muscle (SOL and EDL) was dissected from Long Evans rats and incubated for 60
min in Sigma Medium-199 (resting tension (lg). bubbled with 95:5% 02:C02, 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± 1 0 Osm) (CON) served as a control (n= 17.19.17). Following incubation,
relative muscle water content decreased with HYPER and increased with HYPO in both
muscle types (p<0.05). The cross-sectional area of HYPO SOL type I and type II fibres
increased (p<0.05) while the EDL type 11 fibre area decreased in HYPER and increascd
from HYPO exposure. Furthermore, HYPER exposure in both muscles lead to decreased
ATP and phosphocreatine (p<0.05) and increased creatine and lactate (p<0.05) compared
to CON. This isolated skeletal muscle model proved viable and demonstrated that
altering extracellular osmolality could cause acutc alterations in muscle water content and
resting muscle metabolism.
