Effects of ischemia-reperfusion injury on contractile properties of mouse skeletal muscles

Ischemia and reperfusion are known to be deleterious to skeletal muscle and nerve function. This study investigated the recovery ot isometric contractile function in mice following tourniquet ischemia and the influence of fiber type on these effects. Contractile properties of the soleus (slow twitch) and extensor digitorum tongus (EDL, last twitch) muscles of male C57/BL mice (N-11 ) of age 4-6 months were measured. Mice were killed by cervical dislocation and muscles were excised 2 hours, 3 days, 7 days and 14 days following 3 hours of tourniquet ischemia of the mouse hindlimb. Muscle performance was measured under isometric conditions to determine twitch (kg/cm2), tetanus (kg/cm2), hall relaxation time (msec), contraction time (msec) and Index of fatigue. Maximum tetanus tension for both muscles was significantly different from control at 2 hours, 3 days and 7 days. At 14 days the EDL muscles were significantly different from controls whereas values for soleus muscles were similar to control values. Muscle fatigue index for the EDL increased significantly from 0.15+0.02 in control muscles to 0 6310.01 in experimental muscles at 7 days and from 0.22±0.03 in control muscles to 0.46±0.02 in experimental muscles at 14 days. This phenomenon was not seen in soleus muscles. The data suggest skeletal muscle fiber type may have significant effects on responses to ischemia-reperfusion injury. Importantly, fast twitch muscles may become less fatlgable following ischemia-reperfusion injury.