The effect of fMLP on the distribution of neutrophils in the blood (A), the BM (B), and the pulmonary capillaries (C).

Neither the fMLP-induced fall in the circulating neutrophil counts nor the venous-arterial gradient was inhibited by pretreatment with colchicine (A). fMLP induced a release of mature neutrophils from the BM as demonstrated by the decrease in the volume fraction of the BM cavity occupied by neutrophils (B), which was not inhibited by pretreatment of rats with colchicine (B). fMLP induced neutrophil sequestration within the pulmonary capillaries, and this sequestration was not inhibited by colchicine (C). Colchicine itself induced a decrease in the number of neutrophils circulating within the blood, which was accompanied by an increase in the number of neutrophils sequestered within the capillaries. n = 5 rats in each group; *, significantly different from animals given an infusion of saline compared with fMLP (P < .05); ‡, significantly different from arterial counts (P < .05); and +, significantly different from saline pretreated rats (P < .05).