EFFECT OF METABOLIC INHIBITORS UPON IODIDE TRANSPORT IN SHEEP THYROID SLICES*†

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Abstract
Slices of sheep thyroid glands were incubated in solutions containing serial dilutions of various metabolic inhibitors in addition to concentrations of 1-methyl-2-mercaptoimidazole sufficient to eliminate organic iodinations. Inhibitory patterns were defined by measuring the accumulation of inorganic I131 and the cellular consumption of O2. The available data do not justify an integrated formulation of the mechanism for thyroidal transport of iodide, but certain preliminary conclusions may be derived. Establishment of concentration differentials for iodide requires energy which is generated by cellular aerobic oxidations and channeled through high-energy phosphate bonds. Thus, thyroidal iodide transport can be interrupted by inhibitors which interfere with aerobic metabolism, or which dissociate phosphorylation from oxidation. Sulfhydryl reagents and certain monovalent anions apparently affect other components of the transport system. Specific inhibitors of carbonic anhydrase and alkaline phosphatase do not limit the accumulation of inorganic iodide in thyroid slices.