The effect of certain variables on the tumor and tissue distribution of tracers V: false carrier effect, II, Fe.

The effect of Fe3+ citrate on carrier-free 67Ga and 59Fe kinetics was studied in a Buffalo rat-Morris 7777 hepatoma model. Two mg Fe3+ citrate/Kg were administered intravenously in a variety of time sequences, prior to and following the tracers, and the rats were killed at 4 or 24 hours. 67Ga concentrations could be increased in tumor and decreased in most normal tissues. Administering Fe3+ both one half hour before and 2 hours after the tracers produced 67Ga values equivalent to 72-hour carrier-free values after 4 hours, while simultaneously decreasing gut secretion and increasing urinary excretion. The 59Fe and 67Ga kinetics suggested that events at both vascular and cellular levels were responsible for these changes. This study demonstrated the potential utility of Fe3+ citrate for improving both conventional 67Ga and positron (68Ga) imaging of tumors.