Conversion of Thyroxine to Triiodothyronine by Cultured Human Cells

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Science  09 Mar 1973:
Vol. 179, Issue 4077, pp. 1000-1001
DOI: 10.1126/science.179.4077.1000


Human liver and kidney cells convert 6 to 10 percent of added thyroxine to triiodothyronine in vitro at 37°C. This extent of conversion is ten times greater than that in control studies with killed cells. Conversion is evident within 10 minutes and appears to be maximal within 1 hour. Greater net triiodothyronine formation results if greater amounts of exogenous thyroxine are added to the system, with no plateau evident even at very high thyroxine concentrations. The addition of high concentrations of nonradioactive triiodothyronine resulted in no evident inhibition of the conversion.