SKELETAL-MUSCLE ISCHEMIA-REPERFUSION CAUSES TRANSITORY INCREASE IN MICROVASCULAR PROTEIN PERMEABILITY

The aim of this study was to determine whether the length of ischemia in skeletal muscle influences the return of normal microvascular perme ability during reperfusion in addition to influencing the size of the initial changes. In anesthetized rabbits, the transvascular clearance of labeled albumin was measured in the gastrocnemius and soleus muscle s during the first, second, third, or fourth hour of reperfusion after 1, 2, 3, or 4 h of ischemia. The size of the increases in albumin cle arance, tissue water, and myeloperoxidase activity during the first ho ur of reperfusion was dependent on the length of ischemia. The return of the albumin clearance to control values during the fourth hour of r eperfusion was independent of the length of ischemia. Tissue water, ex travascular mass of native albumin, and myeloperoxidase activity remai ned elevated during the 4 h of reperfusion. After 4 h of ischemia, til e solvent-drag reflection coefficient for albumin was significantly le ss than control during the first hour of reperfusion. The value during the fourth hour of reperfusion was not significantly different from c ontrol. These results suggest that the inflammatory mediators producin g a change in permeability are washed out of the microvasculature duri ng the first few hours of reperfusion.