Activation-induced mobilization of secretory vesicles in bovine neutrophils.
OBJECTIVE
To characterize mobilization of secretory granules in bovine neutrophils.


METHODS
Neutrophils obtained from four 6- to 18-month-old Holstein cattle.


METHODS
Mobilization of secretory granules in bovine neutrophils was determined by measuring changes in cell-surface alkaline phosphatase activity on cells treated with various inflammatory mediators. Subcellular distribution of the alkaline phosphatase activity was determined by analysis of bovine neutrophil homogenates fractionated on density gradients.


RESULTS
Alkaline phosphatase-containing secretory granules of bovine neutrophils were readily mobilized by a number of inflammatory agents, including platelet-activating factor, interleukin-8, tumor necrosis factor-alpha, lipopolysaccharide, leukotriene B4, and zymosan-activated plasma. In contrast, N-formyl-methionyl-leucyl-phenylalanine did not have a significant effect. Phorbol myristate acetate induced a biphasic response with up-regulation of cell-surface alkaline phosphatase at low doses and a return to baseline or even a reduction in cell-surface alkaline phosphatase at higher doses (> or = 10 ng/ml). Subcellular fractionation of bovine neutrophil homogenates revealed that alkaline phosphatase activity resided in light-density membrane vesicles (ie, location of secretory granules), which were distinct from specific, azurophil, and large granules.


CONCLUSIONS
Bovine neutrophils respond to various inflammatory mediators by mobilizing alkaline phosphatase-containing secretory granules. This suggests that the process is an important early step in the host-defense response of bovine neutrophils.
Swain
S D
SD
Department of Veterinary Molecular Biology, Montana State University, Bozeman 59717, USA.
Siemsen
D W
DW
Hanson
A J
AJ
Quinn
M T
MT
D000469:Alkaline Phosphatase / Q000032:analysis / Q000096:biosynthesis*; D000818:Animals; D002417:Cattle / Q000276:immunology*; D018836:Inflammation Mediators / Q000276:immunology* / Q000494:pharmacology; D016209:Interleukin-8 / Q000276:immunology / Q000494:pharmacology; D007975:Leukotriene B4 / Q000276:immunology / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000276:immunology / Q000494:pharmacology; D009504:Neutrophils / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D009195:Peroxidase / Q000032:analysis / Q000096:biosynthesis; D010972:Platelet Activating Factor / Q000276:immunology / Q000494:pharmacology; D022142:Secretory Vesicles / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000276:immunology / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000494:pharmacology
D018836:Inflammation Mediators; D016209:Interleukin-8; D008070:Lipopolysaccharides; D010972:Platelet Activating Factor; D014409:Tumor Necrosis Factor-alpha; D007975:Leukotriene B4; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009195:Peroxidase; D000469:Alkaline Phosphatase; D013755:Tetradecanoylphorbol Acetate