Abstract
Summary
1. The effect of free iodide (Nal or KI) and phenothiazine N.F. (green) on the suppression of I131 uptake by thyroid in rats is studied and compared. Various related compounds and derivatives of phenothiazine are also surveyed. 2. Column chromatographic fractionation of phenothiazine N.F. (green) reveals that the activity described is strongly associated with its iodine content; however, phenothiazine N.F. (purified) with negligible amounts of iodine has some suppressing quality. 3. In continuous feeding experiments phenothiazine N.F. (green) when given in doses sufficient to partially suppress I131 uptake did not affect the weight of the thyroid gland, total body weight or any of the other organs studied. No component of phenothiazine N.F. (green) is goitrogenic. 4. A chromatographic method is described for studying the renal excretory levels of free iodide after rats are treated with Nal, phenothiazine N.F. (green) or a combination of both. Those animals receiving Nal or Nal and phenothiazine N.F. (green) showed an equal but elevated level of iodide excretion. Those rats given phenothiazine N.F. (green) alone had little or no iodide in their urine over a 24-hour period. 5. It is concluded that the effect of phenothiazine N.F. (green) on reducing the uptake of I131 by the rat thyroid is not due solely to the availability of free iodide to this gland as a result of dissociation from an organic combination.
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