PROTEASE INHIBITION ATTENUATES MICROVASCULAR DYSFUNCTION IN POSTISCHEMIC SKELETAL-MUSCLE

Neutrophils accumulate in skeletal muscle subjected to ischemia-reperf usion and appear to contribute to reperfusion induced microvascular dy sfunction. The overall objective of this study was to assess the role of the neutrophilic hydrolytic enzyme elastase in ischemia-reperfusion -induced granulocyte accumulation and microvascular dysfunction in ske letal muscle. We examined the effect of three structurally unrelated e lastase inhibitors [eglin C, MeOsuc-Ala-Ala-Val-CH2Cl (MAAPV), or L-65 8758], administered at the onset of reperfusion, on neutrophil content and the increase in microvascular permeability induced by 4 h of isch emia and 0.5 h of reperfusion in the isolated canine gracilis muscle. Changes in vascular permeability (1 - sigma) were assessed by determin ing the solvent drag reflection coefficient for total plasma proteins (a) in the following groups: 1) 4.5 h of continuous perfusion (nonisch emic), 2) ischemia-reperfusion alone, 3) ischemia-reperfusion + eglin C, 4) ischemia-reperfusion + MAAPV, and 5) ischemia-reperfusion + L-65 8758. Muscle neutrophil content was monitored by assessing tissue myel operoxidase (MPG) activity in biopsies obtained at the end of the expe riments. In nonischemic muscles, 1 - a and MPO activity averaged 0.13 +/- 0.03 and 0.7 +/- 0.2 units/g wet wt, respectively. Ischemia-reperf usion was associated with marked increases in microvascular permeabili ty (1 - sigma = 0.39 +/- 0.02) and muscle MPO activity (8.9 +/- 1.2 un its/g wet wt) that were attenuated by eglin C, MAAPV, and L-658758 (1 - sigma = 0.21 +/- 0.01, 0.22 +/- 0.02, and 0.21 +/- 0.03, respectivel y; MPO activity = 2.7 +/- 0.4, 2.1 +/- 0.8, and 2.8 +/- 1.8 units/g we t wt, respectively). These results suggest that granulocyte accumulati on in postischemic skeletal muscle is dependent on the release of elas tase from activated phagocytic cells. Moreover, neutrophilic elastase appears to play a major role in reperfusion-induced increases in micro vascular permeability in skeletal muscle.