Response of white blood cells to iodipamide ethyl ester particles.

The effect of intravenously injected iodipamide ethyl ester (IDE) particles (150 mgl/kg) on white blood cells was studied by light and electron microscopy. The clearance of IDE from rat plasma also was determined by analyzing free IDE particles in a counting chamber. The total white blood cell count remained essentially unchanged up to 40 minutes after the IDE injection, but the polymorphonuclear (PMN) neutrophil count decreased significantly. At 5 minutes postinjection, occasional PMNs contained ingested IDE particles, but by 40 minutes no intracellular particles could be found in the peripheral circulation. In vitro incubation experiments confirmed that human PMNs ingest IDE particles. In electron microscopy, the cells and particles seemed to be morphologically intact. Of the IDE particles counted at 5 minutes postinjection, only 4% remained in plasma at 30 minutes and none at 40 minutes. The decrease in PMN count apparently reflects sequestration of phagocytic cells from the circulation.