Swain SD, Siemsen DW, Hanson AJ, Quinn MT. Activation-induced mobilization of secretory vesicles in bovine neutrophils.
Am J Vet Res 2001;
62:1776-81. [PMID:
11703023 DOI:
10.2460/ajvr.2001.62.1776]
[Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE
To characterize mobilization of secretory granules in bovine neutrophils.
SAMPLE POPULATION
Neutrophils obtained from four 6- to 18-month-old Holstein cattle.
PROCEDURE
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 AND CLINICAL RELEVANCE
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.
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