Effect of Amphotericin B on Thyroidal Iodide Concentration1

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Abstract
The effect of ampho-tericin B on Na+ and K+ concentration and iodide tissue/medium ratio (T/M I) of beef thyroid slices in vitro has been studied. Amphotericin B in concentrations from 2.5 to 50 ug/ml regularly decreased thyroidal T/M I and K+ concentration and increased thyroidal Na+ concentration. This effect was reversible by washout and by incubation in medium containing 16 [image][image]/l of K+, but was not altered by change in medium Na+. The addition of cholesterol to the medium had no intrinsic effect on T/M I but inhibited the action of amphotericin B on T/M I. Incubation with amphotericin B did not cause reduction in the ouabain-sensitive ATPase of beef thyroid nuclear fraction. It also did not lower O2 consumption of thyroid slices. These findings lead to the conclusions that amphotericin B acts on the thyroid cell membrane and does ao in a fashion different from ouabain. This is further evidence against the concept that operation of Na+, K+ -activated ATPase is a sufficient condition for thyroidal iodide transport.