Uptake and dissolution of particulate iodipamide ethyl ester in the spleen. A morphologic study.

Iodipamide ethyl ester (IDE) is an experimental particulate contrast agent being developed for CT image enhancement of the liver and spleen. IDE particles are phagocytized by the reticuloendothelial cells after an intravenous injection. The uptake and dissolution of IDE particles were studied in the spleen with light and electron microscopy. Two minutes after injection, intra- and extracellular IDE particles were found in the red pulp of the spleen. Highest concentration of IDE was seen in the marginal zone surrounding the white pulp. Particles also were seen elsewhere in the red pulp but only occasionally between the outermost cells of the white pulp. The extracellular particles disappeared within 4 hours postinjection. At one day postinjection, the amount of intracellular IDE particles had begun to decrease. Electron micrographs showed that the intracellular particles dissolved gradually in the phagocytes and caused transient degenerative morphologic changes. At three days postinjection, practically all IDE particles had disappeared from the spleen. Polystyrene latex particles were used as controls. They were phagocytized like the IDE particles, but they did not disappear from the phagocytes. IDE particles caused no morphologic injuries in nonphagocytic cells of the spleen.