Synthesis of 6-radioiodo-6-deoxy-d-galactose, and its tissue distribution and excretion in rats

6-Radioiodo-6-deoxy-D-galactose was prepared by thermal neutron irradiation of the non-radioactive compound, and by iodine exchange on 6-iodo-1,2:3,4-diisopropylidene-6-deoxygalactose with either NaI-125, NaI-131 and MgSO4, or I-123 on gold foil. The diisopropylidene compound ws deblocked with aqueous acid to obtain the labeled sugar. Upon IV injection of I-125 or I-131 labeled 6-iodo-6-deoxygalactose into rats, rapid renal and heptic uptake resulted in elimination of 22% and 36% of the dose in 4 hour bile and 4 hour urine respectively. About 2% of a dose remained in the bodies of iodide pretreated rats, 24 hours after injection. After 4 hours, tissue: blood ratios ranged from 0.3 (Skeletal muscle) to 3.8 (kidney). Although iodogalactose was found to be stable in saline at room temperature, label integrity in vivo was compromised after about 4 hours. Bile contained primarily free radioiodide, whereas urine contained mainly radioiodogalactose with varying proportions of radioiodide