ENZYME-RELEASE BY BOVINE NEUTROPHILS

Release of enzymes from cytoplasmic granules has been postulated to ha ve a major role in neutrophil-mediated tissue injury. Secretion or rel ease of primary granules, specific granules, and cytosolic enzymes by bovine neutrophils was examined by quan tifying the release of beta-gl ucuronidase, B-12-binding protein, and lactate dehydrogenase, respecti vely, in response to predetermined amounts of phorbol myristate acetat e, calcium ionophore, and opsonized zymosan. These responses were comp ared with the enzyme release induced by exposure to live or dead, unop sonized or opsonized Pasteurella haemolytica. The greatest release of beta-glucuronidase, B-12-binding protein, and lactate dehydrogenase wa s observed in neutrophils exposed to live organisms partially because of neutrophil lysis. Bovine neutrophils respond markedly to particulat e agonists, live or dead, pathogenic or nonpathogenic, by a selective release of specific granules, an effect enhanced by opsonization. Part iculate agonists induce minimal primary granule release other than tha t induced by cell death. Because bovine neutrophils contain quantitati vely high numbers of specific granules, the high rate of secretion/rel ease in response to P haemolytica organisms could have a major role in the tissue responses that characterize the lesions of pneumonic paste urellosis.