Indium-111-labeled cellular blood components: mechanism of labeling and intracellular location in human neutrophils.

Human neutrophils were labeled with In-111 oxine by incubation at room temperature, and the fate of the oxine and the intracellular location of the In-111 were determined. Neutral (1:3) In-111 oxine complex diffuses rapidly across the cell membrane and then dissociates. Some of the oxine leaves the cell and the In-111 binds intracellularly. After short periods of incubation the label is distributed mostly to four soluble components, a small proportion of which had a distribution similar to that of specific and azurophil granules. After longer incubation periods there was relatively less radioactivity with the soluble components and probably more attached to the particulate material. A small peak of radioactivity also appeared in the region of DNA distribution, but no confirmation could be obtained for the association of the In-111 radioactivity with DNA.