Uptake of 131 by Rat Organs and Body Fluids Following Injection of Different I 131 Preparations. ∗

Abstract

Summary

An “extraneous” I¹³¹ component identical with component “S” of Ahn and Rosenberg or “U” of Taurog was isolated from cysteine-free radioiodide preparations (obtained from E. R. Squibb & Sons) by a chromatographic separation and elution procedure described earlier.

One microcurie of NaI¹³¹ or of “extraneous” I¹³¹ were injected intraperitoneally into adult female rats. At the end of 1, 3 and 24 hours after injection, the animals were killed and the uptake of radioactivity in various organs and body fluids was measured. The results show that at one and 3 hours following injection, the uptake of NaI¹³¹ by stomach, thyroid, liver, intestine and plasma was significantly higher than the uptake of “extraneous” I¹³¹. However, during the same period, urinary excretion of both the compounds remained the same. At 24 hours following injection of either NaI¹³¹ or “extraneous” I¹³¹ there was a significant lowering of radioactivity in stomach, liver, intestine and plasma and there were no significant differences in uptake of NaI¹³¹ or “extraneous” I¹³¹. However, the thyroid gland continued to show an increased uptake of both NaI¹³¹ and “extraneous” I¹³¹ at 24 hours and also a significantly higher uptake of NaI¹³¹ in comparison to “extraneous” I¹³¹. The results on the radioautography of one-hour urine samples from rats receiving an injection of “extreneous” I¹³¹ showed the presence of “extraneous” I¹³¹ to the extent of 50% of total I¹³¹ excreted. This would indicate that “extraneous” I¹³¹ is not rapidly reduced to iodide in a manner similar to that reported for iodate.