形態・生理1

[IV-16-17] Suppression of neutrophil phagocytosis in mastitic milk

*Masato Hirano¹, Keiichi Hisaeda², Yusaku Tsugami¹, Takahiro Nii¹, Naoki Suzuki¹, Naoki Isobe¹ (1. Hiroshima Univ., 2. Okayama Univ of Sci.)

[Objective] After collecting mastitic milk, the viable bacterial count decreases dramatically during its preservation by the neutrophil phagocytosis. The aim of the present study was to investigate whether neutrophil phagocytosis can be suppressed by colchicine. [Method] Milk was collected 24 h after lipopolysaccharide was intramammary infused in Tokara and Shiba goat, and centrifuged to separate neutrophils. Then 0, 0.1 and 1 mg/mL of colchicine and 2.0×10⁷cell/mL of inactivated Escherichia coli (EC) or Staphylococcus aureus (SA) were added into neutrophils and the mixture was incubated at 37 ℃ for 30 min. The mixture was smeared on a slide glass, followed by Giemsa staining. [Result] Percentage of neutrophils that phagocytosed EC or SA were significantly lower in both the colchicine 0.1 and 1 mg/mL groups than in control group. The number of bacteria in a neutrophil was also significantly lower in both colchicine groups. These results suggest that the colchicine can inhibit the neutrophil phagocytosis, which enables bacterial examination from mastitic milk.