Improved method for quantification of tissue PMN accumulation measured by myeloperoxidase activity

Myeloperoxidase (MPO) was used as a marker enzyme for measuring polymorphonuclear leukocyte (PMN) accumulation in tissue samples. The MPO recovery from kidney, liver, myocardium, skeletal muscle (iliopsoas), and skin was measured, and a variation of 5%-100% was found, depending on the tissue analyzed. The recovery could be improved to 100% in all tissues by incubation of the tissue samples at 60 degrees C for 2 hr. This improved method was used to measure PMN accumulation in rabbit myocardium after regional ischemia and reperfusion. The MPO activity increased fivefold in the occluded area as compared with intact myocardium. Treatment with IB4, a monoclonal antibody recognizing the leukocyte adhesion molecule Mac-1, decreased the MPO activity in the occluded area almost to the level in intact myocardium.