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JANE HALPERN, PATRICIA M. HINKLE, EVIDENCE FOR AN ACTIVE STEP IN THYROID HORMONE TRANSPORT TO NUCLEI: DRUG INHIBITION OF L-125I-TRIIODOTHYRONINE BINDING TO NUCLEAR RECEPTORS IN RAT PITUITARY TUMOR CELLS, Endocrinology, Volume 110, Issue 3, 1 March 1982, Pages 1070–1072, https://doi.org/10.1210/endo-110-3-1070
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When added to intact GH4C1 or GH3 cells, cytochalasin b, dansylcadaverine, and chloroquine inhibited the binding of L-125I-triiodothyronine (T3) to nuclear receptors within 30 min. These drugs also reduced the amount of 5 I-T3 in the post-nuclear supernatant fraction of cells lysed with Triton χ-100. If 125I-T3 was added before the drugs, 125I-T3 that was already bound did not dissociate, but further binding was blocked. Inhibition due to 10 μM cytochalasin b or 150 yM dansylcadaverine was reversible within 2 h of drug removal, and inhibition due to 150 μM chloroquine was partially reversible. Drug inhibition was overcome as the T3 concentration was raised. These drugs did not significantly inhibit 125I-T3 binding to isolated nuclei, and nuclei isolated from drug-treated cultures bound as much 125I-T3 as control nuclei. The results suggest that thyroid hormones reach their nuclear binding sites by an active transport process which is inhibited by the drugs studied.
