Metabolic responses in feline "red" and "white" skeletal muscle to shock and ischemia.

In order to investigate possible differences in the reaction to hypoxic conditions between "red" and "white" skeletal muscle, cats were subjected to a 2 h period of either hemorrhagic shock or hind limb tourniquet ischemia, and the hypoxia induced changes were studied in the soleus and lateral gastrocnemius muscles. Muscle biopsies were analysed for ATP, CP, glucose, G 6-P and lactate. Using microelectrodes, the resting membrane potential was repeatedly measured. Both experimental models resulted in increased tissue lactate levels and a successive decrease in the membrane potential of both muscles studied. No reduction of the high energy phosphagen content (ATP + CP) occurred in any of the muscles during shock. The tourniquet ischemia resulted in a 40% reduction of the ATP + CP content in the soleus muscle, whereas in the gastrocnemius muscle no significant reduction occurred. A significant correlation was found between the tissue lactate content and the membrane potential under both conditions and in both muscles studied. It is concluded that "red" muscles are more susceptible to metabolic derangement than "white" muscles during total ischemia, whereas during hypovolemia "red" muscles appear to be protected from early hypoxic damage, probably due to a redistribution of skeletal muscle blood flow.