Abstract:
The purpose of this study was to examine cell glucose kinetics in rat skeletal
muscle during iso-osmotic recovery from hyper- and hypo-osmotic stress. Rat
EDL muscles were incubated for sixty minutes in either HYPO (190 mmol/kg),
ISO (290 mmol/kg), or HYPER (400 mmol/kg) media (Sigma medium-199, 8 mM
glucose) according to an established in vitro whole muscle model. In addition to
sixty minute baseline measures in aniso-osmotic conditions, (HYPO-0 n=8; ISO-
0, n=S; HYPER-0, n=8), muscles were subjected to either one minute (HYPO-1
n=8; ISO-1, n=8; HYPER-1, n=8) or five minutes (HYPO-5 n=8; ISO-5, n=8;
HYPER-5, n=8) of iso-osmotic recovery media and analyzed for metabolite
content and glycogen synthase percent activation. To determine glucose uptake
during iso-osmotic recovery, muscles (n=6 per group) were incubated for sixty
minutes in either hypo-, iso-, or hyper-osmotic media immediately followed by
five minutes of iso-osmotic media containing
3H-glucose and 14
C-mannitol.
Increased relative water content/decreased [glucose] (observed in HYPO-0) and
decreased water content/increased [glucose] (observed in HYPER-0) returned to
ISO levels within 5 minutes of recovery. Glycogen synthase percent activation
increased significantly in HYPO-5 over iso-osmotic controls. Glucose uptake
measurements revealed no significant differences between groups. It was
determined that [glucose] and muscle water content rapidly recovered from
osmotic stress demonstrating skeletal muscle's resilience to osmotic stress.
