Neutrophil antiserum response to decrease in proteolytic activity in loaded rat muscle

The leukocytes that are found in skeletal muscles after intense muscular ac tivity have been shown to infiltrate areas of injury in skeletal muscle tis sue. We believe that leukocyte enzymes, which appear in the tissue after th e degranulation or destruction of leukocytes, could play a role in tissue e nzyme activities. Neutrophil proteinases were investigated, Histological da ta provided evidence of rat muscular tissue infiltration by leukocytes afte r intense physical loading. To reduce the influx of leukocytes in rat muscl es, a rabbit antiserum against rat peritoneal leukocytes was injected into rats after muscle loading. This resulted in a reduction in muscle cytosol p roteolytic activity as compared to control animals (who received saline inj ections), The levels of proteolytic activities of media conditioned by the soleus muscle isolated from antiserum-treated rats were also reduced. These data provide evidence that the increase in proteolytic activity observed i n rat skeletal muscles after physical loading is partially induced by neutr ophil proteinases.