The effect of pretreating rats with colchicine on BM release induced by infusion of fMLP in rats.

The circulating neutrophil counts in rats pretreated with saline decreased in both arterial and venous samples within 5 minutes of infusion (A). By 10 minutes, there was a significant increase in the number of neutrophils within the venous blood sample. This increase was not observed in the arterial blood sample. This venous-arterial gradient in neutrophil concentration measured BM release.1Pretreatment with colchicine induced a fall in the circulating neutrophil counts to approximately 50% of baseline value (B). However, infusion of fMLP induced a similar fall in the circulating neutrophil counts and a similar venous-arterial gradient (B) as observed in animals that did not receive colchicine. When rats received a second dose of colchicine 2 hours after the first, no fall in circulating neutrophil counts occurred (C). This dosing regimen also did not inhibit the fMLP-induced decrease in circulating neutrophil counts or the venous-arterial gradient compared with animals given saline (D). n = 5 rats in each group; *, significantly greater than values in the arterial blood at this time point, P < .05.