5,5'-Diphenylhydantoin decreases the entry of 3,5,3'-triiodo-L-thyronine but not L-thyroxine in cultured GH-producing cells

L. R. Zemel, D. R. Biezunski, L. E. Shapiro, M. I. Surks

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We determined the effect of 5,5'-diphenylhydantoin (DPH) on the kinetics of T3 and T4 uptake in cultured GH-producing (GC) cells under serum-free conditions. GC cells accumulated [125I]T3 at a greater fractional rate than [125I]T4. The t( 1/2 ) of exit of [125I]T4 and [125I]T3 previously equilibrated in GC cells was 28 min for T4 and 66 min for T3. T3 and T4 entry rates were not influenced by up to a 10,000-fold molar excess of nonradioactive T3, T4, d-T4, rT3, 3,5-T2 and diiodotyrosine. Thus, entry of T3 and T4 in GC cells appeared nonsaturable and was not influenced by various thyroid hormone analogues. DPH, 25-200 μmol/l, decreased the rate of T3 entry in a dose-dependent manner and did not influence the T3 exit rate. At 200 μmol/l DPH T3 entry decreased by 40%. Rates of entry and exit of T4 were unaffected by DPH. DPH may affect T3 and T4 entry differentially at the level of the plasma membrane.

Original languageEnglish (US)
Pages (from-to)392-398
Number of pages7
JournalActa Endocrinologica
Issue number3
Publication statusPublished - Jan 1 1988


ASJC Scopus subject areas

  • Endocrinology

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