Induction of Nitric Oxide Production by Bovine Mammary Epithelial Cells and Blood Leukocytes

摘要

A recent study from our laboratory has shown that significant amounts of nitric oxide are released by so- matic cells recovered during endotoxin-induced masti- tis. The present study was undertaken to investigate which cell type(s) among milk somatic cell population can produce nitric oxide under inflammatory condi- tions. Nitric oxide release from mammary epithelial cell lines and from bovine neutrophils and monocytes extracted from blood was measured in response to cy- tokines and Escherichia coli lipopolysaccharides. An epithelial cell line isolated from bovine mammary gland, FbE cells, was found to release nitric oxide after exposure to interleukin-1 beta. This nitric oxide production was completely abolished by addition of L-N6-(1-iminoe- thyl) lysine, a potent inducible nitric oxide synthase inhibitor. Bovine monocytes produced nitric oxide in response to recombinant bovine interferon-gamma alone or in combination with E. coli lipopolysaccharides. In these cells, nitric oxide release was reduced by the addition of inducible nitric oxide synthase inhibitors L-N~6-(1- iminoethyl) lysine and aminoguanidine. Lipopolysac- charides and recombinant bovine interferon-gamma in- creased nitric oxide synthase mRNA in neutrophils, but nitric oxide release could not be detected under any of the experimental conditions used. These results show that bovine epithelial cells and mononuclear phago- cytes produce nitric oxide under inflammatory condi- tions and suggest that these cell populations are respon- sible for nitric oxide release observed during mastitis.