POSTISCHEMIC EXTREMITIES EXHIBIT IMMEDIATE-RELEASE OF TUMOR-NECROSIS-FACTOR

Purpose: Although reperfusion of acutely ischemic extremities can caus e cardiopulmonary collapse and death, the humoral agent(s) released fr om limbs promoting this distant organ injury are not well characterize d. We hypothesized that tumor necrosis factor-alpha (TNF-alpha), a cyt okine that causes cardiopulmonary dysfunction in septic shock, may be released from postischemic extremities. Methods: Isolated rat hindlimb s were perfused at constant pressure with a nonrecirculating crystallo id-based buffer. After 60 or 120 minutes of normothermic ischemia, TNF activity was measured in sequential samples of venous effluent by L92 9 bioassay. Associated limb injury was assessed by the extent of no-re flow after reperfusion, changes in endothelial permeability to iodine 125-labeled albumin and skeletal muscle injury by uptake of technetium 99 pyrophosphate.Results: After 120 minutes of normothermic ischemia (n = 10), a 15-fold increase in TNF-alpha activity in venous effluent occurred, with peak activity at 1.5 minutes of reperfusion (30.6 +/- 8 .7 U/ml) falling to near control levels by 5 minutes. This group had a 3.3-fold increase in vascular permeability, a 2.2-fold increase in th e muscle injury index and a 71.2% decline in reperfusion flow (all p < 0.05 vs control). Pretreatment of extremities with an anti-TNF-alpha antibody in a second group of limbs undergoing 120 minutes of ischemia (n = 10) decreased TNF activity to levels not significantly different from the nonischemic control group (n = 12). The extent of no-reflow in limbs treated with antibodies was significantly attenuated (flow 44 .9% of control vs 29.8% [untreated], p < 0.05). Antibody treatment aff ected neither muscle injury nor vascular permeability. Conclusions: Po stischemic extremities exhibited a transient, early burst of TNF relea se on reperfusion, which likely represented washout of TNF produced du ring ischemia. Suppression of TNF activity with an antibody to TNF-alp ha resulted in a salutary increase in postischemic flow rates, suggest ing that TNF may play a role in the no-reflow phenomenon.