Abstract:
This study investigated the regulation of carbohydrate metabolism through changes in
skeletal muscle cell volume immediately post contraction and during recovery. Using an
established in vitro isolated muscle strip model, soleus (SOL) and extensor digitorum
longus (EDL) were dissected from male rats and incubated in an organ bath (perfused
with 95% O2; 5% CO2, pH 7.4, temperature 25°C) containing medium- 199 altered to a
target osmotic condition (iso-, hypo- or hyper-osmotic; 290, 1 80, 400 mmol/kg). Muscles
were stimulated for 10 minutes (40 Hz SOL; 30 Hz EDL) and then either immediately
flash frozen or allowed to recover for 20 minutes before subsequent metabolite and
enzyme analysis. Results demonstrated a relative water decrease in HYPER vs. HYPOosmotic
condition (n=8/group; p<0.05) regardless of muscle type. Specifically, the SOL
HYPER condition had elevated metabolite concentrations after 10 minutes of stimulation
in comparison to both HYPO and ISO (p<0.05), while EDL muscle did not show any
significant difTerences between the HYPER or HYPO conditions. After 20 minutes of
recovery, metabolic changes occurred in both SOL and EDL with the SOL HYPER
condition showing greater relative changes in metabolite concentrations versus HYPO.
The results of the current study have demonstrated that osmotic imbalance induces
metabolic change within the skeletal muscle cell and muscle type may influence the
mechanisms utilized for cell volume regulation.
