STUDIES ON THE FIXATION OF RADIOACTIVE IODINE BY THE RABBIT THYROID1

Abstract

Doses of 35 [gamma] iodide (in the form of KI), with quantities of radioactive iodide added as a tracer, were injected intraven. into normal [male] rabbits. At various time intervals after inj., the animals were sacrificed and their thyroids were removed for frac-tionation. Fractionation was accomplished by extracting with acetone which dissolves the inorganic iodide while proten I remains in the insoluble fraction. Each fraction was analyzed for radioactivity and for total I. The uptake of iodide by the thyroid during the first few mins. fol-lowing the inj. was extremely rapid. This initial rapid accumulation of I occurred in the acetone soluble (inorganic) fraction and reached a peak in 10 mins., after which time the radioactive I content of this fraction decreased. Tagged I may be found in the acetone insoluble fraction within 5 mins. following the iodide adm. and ac-cumulates over a period of several hrs.