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To investigate the effect of iron deficiency on the biodistribution and tumor uptake of Ga-67 citrate, 20 weanling Sprague-Dawley rats were maintained for 6-8 wk on a low-iron diet. Eighteen littermates were maintained on a normal iron diet and served as controls. Animals received 10 microCi Ga-67 citrate, and urine and feces were collected for 48 hr. The animals were then killed, tissue samples were obtained, and serum iron and unsaturated iron-binding capacity (UIBC) were measured. The accumulation of Ga-67 in the liver and spleen (% ID/g) was markedly increased in iron-deficient animals and urinary excretion was reduced. Tumor uptake was not significantly different in iron-deficient and control animals, but tumor-to-blood ratios were elevated (p.001) in the iron-deficient animals because of low blood levels of Ga-67. The liver and spleen accumulation of Ga-67 correlated significantly (p.001) with the UIBC. The results show that iron deficiency alters the distribution of Ga-67 citrate, and suggest that the variable liver-spleen uptake seen in clinical Ga-67 images may be explained, in part, by changes in serum iron and UIBC. |
