EFFECT OF COLD ON ISCHEMIA-REPERFUSION-INDUCED MICROVASCULAR PERMEABILITY INCREASE IN CAT SKELETAL-MUSCLE

The effects of reduced temperature during ischemia (I) upon microvascular permeability and resistance increases during reperfusion (R) were assessed in skeletal muscle. Protein solvent-drag reflection coefficients (sigma(f)) and changes in vascular resistance were measured during 37 degrees C reperfusion of isolated, whole-blood perfused cat hindlimbs after the limbs had been subjected to 3.5 h of ischemia at several temperatures. sigma(f) was determined from the disappearance rates of water and protein from the circulating perfusate during a period of induced microvascular fluid filtration. The I/R procedure at 37 degrees C caused sigma(f) to fall from similar to 0.85 to similar to 0.5, indicating a large increase in microvascular permeability. Hypothermic ischemia at 30, 22, 17, or 12 degrees C totally abolished this drop in sigma(f). However, when the ischemia was at similar to 5 degrees C, there was a significant fall in sigma(f) similar to 0.7, which was similar to the value we found previously with 5 h of continuous perfusion at this low temperature. The normothermic I/R procedure led to an increase in vascular resistance of similar to 250% above the value measured prior to I/R. Hypothermic ischemia totally abolished this resistance increase, except for the lowest temperature, for which the increase was 150%. Therefore, hypothermia can prevent the microvascular dysfunction caused by 3.5 h of ischemia at 37 degrees C in this preparation. However, when the temperature was reduced too far (similar to 5 degrees C), a cold injury to the microvascular resulted in permeability and resistance increases. (C) 1994 Academic Press, Inc.