Phospholipid and adenine nucleotide metabolism in muscle after burn injury

The role of phospholipid and adenine nucleotide metabolism in postburn unresponsiveness of muscle to insulin was examined. A single hindlimb scald in the rat was produced, and 3 days later soleus muscles were incubated in vitro with and without insulin. Under basal conditions muscles from the burned limbs had normal contents of phosphatidylcholine and phosphatidylinositol but decreased diphosphatidylglycerol (-39%) and phosphatidylethanolamine (-24%) and increased sphingomyelin (+62%), lysophosphatidylcholine (+68%), and phosphatidylserine (+13%) compared with the contralateral unburned limb. Such muscle also incorporated 107-396% more [32P]phosphate into all measured phospholipids, except for diphosphatidylglycerol. The presence of insulin had no effect on either the mass of phospholipids or 32P incorporation in any muscle. The burned limb muscles (frozen in situ) also exhibited lower levels of ATP (-25%) and total adenine nucleotides (-24%) than uninjured muscle but normal adenylate energy charge. The burned limb muscles had lower adenosine (-37%), but inosine and hypoxanthine were 82 and 39% higher, respectively. These data suggest recovery of muscle from local thermal injury is associated with alterations in mass, and possibly also turnover, of tissue phospholipids, the measured phospholipids do not mediate the postreceptor action of insulin in normal muscle, energy charge of the recovering injured muscle is restored before ATP level at the time when this muscle is unresponsive to insulin stimulation.