Spontaneous leukocyte rolling in rat and mouse microvessels is independent of mast cell activity.

OBJECTIVE AND

DESIGN

The role of mast cells in spontaneous leukocyte rolling in venules of the mouse cremaster muscle and rat mesentery was investigated.

MATERIALS: The experiments were carried out using mast cell-deficient rats (Ws/Ws), WBB6F1 mice (W/Wv), and their congenic littermates (wild type).

TREATMENT: Administration of compound 48/80 intraperitoneally (50 microg) in rats and intrascrotally (5 microg) in mice, 4 h prior to the experiments.

METHODS

Intravital microscopy of the terminal vascular beds in mouse cremaster muscle and rat mesentery.

RESULTS

The level of spontaneous leukocyte rolling and the rolling velocity in venules of mast cell-deficient animals exactly matched that seen in wild-type animals. Challenge with compound 48/80 markedly increased leukocyte adhesion and emigration in venules of wild-type animals. In contrast, the number of adherent and extravascular leukocytes was very low in compound 48/80-challenged animals lacking mast cells and did not differ from that seen in control animals treated with phosphate-buffered saline.

CONCLUSIONS

The presence or activation of mast cells has no bearing on spontaneous leukocyte rolling, at least not in rat and mouse microvessels.