IN VITRO STUDY OF THE ABILITY OF THYROID HOMOGENATE TO CONCENTRATE IODIDE

Abstract

SUMMARY 131I was added to tissue homogenates of rat and dog thyroids in collodion bags and allowed to equilibrate with equal volumes of surrounding buffer solution. No difference in 131I concentration inside and outside the bags was found in experiments in which 10−3 m propylthiouracil was added to the buffer solution. In the absence of propylthiouracil, an increased concentration of 131I was found in the homogenate phase, mostly due to protein precipitable iodine. The results lend no support to the hypothesis which accounts for the high thyroid/serum 131I ratio in vivo by physico-chemical linkage of iodide with specific thyroid protein. From these and the previously described radioautographic findings the iodide concentration by the thyroid in vivo is considered to result from an active transport at the outer cell membrane of the intact follicle.