Effects of Ethionine on Thyroid Function1

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Abstract
Three hr. after injection of DL-ethionine in the rat, thyroid ATP concentration was significantly (p< .01) lowered, the mean value being 0.38 [mu]mole/g, while the control value was 0.66 [mu]mole/g. At this time interval, both T/S [thyroid/serum] and T/M [thyroid medium] radioiodide concentration ratios were also lowered by ethionine injection. Concurrent injection of methionine, adenine or ATP prevented both glandular ATP depletion and reduction of T/S and T/M induced by ethionine alone. Injection of ATP or adenine increased glandular ATP above control values, but did not affect iodide transport. Although ethionine greatly impaired thyroid organisation of administered iodide, it did not prevent injected TSH [thyrotropin] from stimulating organic binding, enhancing thyroid I depletion, or raising the serum PBI concentration. By contrast, ethionine given together with TSH prevented the increment in glandular NADP induced by TSH alone. Reduction of thyroid ATP concentration impairs iodide transport. The stimulatory action of TSH on glandular I organification and release appears to be exerted through a pathway independent of ATP depletion as induced by ethionine.

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