Uptake of L-triiodothyronine into human cultured lymphocytes

Holm, Åsa; Wong, Kam-Fai; Pliam, Nathan B.; Jorgensen, Eugéne C.; Goldfine, Ira D.

doi:10.1530/acta.0.0950350

Cited by 41 publications

(11 citation statements)

References 12 publications

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“…The possible role of the plasma membrane in regulating peripheral thyroid hormone metabolism has been extensively studied (1)(2)(3)(4)(5)(6)(7)(8)(9). A specific hormone uptake has been described in hepatocytes (6), erythrocytes (5), lymphocytes (4), pituicytes (8), and fibroblasts (9).…”

Section: Introductionmentioning

confidence: 99%

“…Thyroid hormone is an amino acid derivative, although apparently not sharing the A system (unpublished data). The (4,400 ,uCi/gg) were purchased from New England Nuclear (Boston, MA). The purity of labeled and unlabeled hormones was assayed by thin-layer chromatography on silica gel KIF (Whatman, Inc., Clifton, NJ) using the solvent system formic acid/methanol/chloroform (1:3:16), according to Sato and Cahnmann (14).…”

Section: Introductionmentioning

confidence: 99%

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Role of sodium in thyroid hormone uptake by rat skeletal muscle.

Centanni

Robbins²

1987

J. Clin. Invest.

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Whether Na+ movement through the plasma membrane plays a role in thyroid hormone uptake was investigated in intact rat soleus muscles. After preincubation for 120 min at 37°C in modified Krebs-Ringer bicarbonate containing 140 or 5 mM Na+ plus choline or lithium to maintain osmolarity, muscles were incubated with 50 pM ['5Iltriiodo-L-thyronine (T3) or L'251L-thyroxine (T4) for 60 min. T3 uptake was decreased when extracellular Na+ was replaced by either choline or lithium, the amount of decrease corresponding to the specific (or saturable) uptake component. Monensin, an ionophore that stimulates Na' entry, increased T3 uptake at 140 mM Na+ but not at 5 mM Na+. Amiloride, a Na+/H+ exchange inhibitor, had no effect on T3 uptake under basal conditions or when Na+ was replaced by choline, but reversed the action of lithium. Ouabain, an inhibitor of Na+/K+ ATPase, reduced specific T3 uptake. T4 uptake was unaffected by low extracellular Na+.These results are consistent with a major role of Na+ movement in T3 uptake by skeletal muscle, but not in T4 uptake, and suggest an involvement of membrane pumps in this process.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of sodium in thyroid hormone uptake by rat skeletal muscle.

Centanni

Robbins²

1987

J. Clin. Invest.

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“…Thyroid hormones (THs) must cross the target cell plasma membrane in order to reach their receptors and metabolizing sites. Several types of cells have specific systems for TH transport (Krenning et al, 1978;Holm et al, 1980;Cheng, 1983;Pontecorvi and Robbins, 1986;Osty et al, 1988). Some studies of metabolic blockers and TH uptake into isolated tissues or cells suggest that Na+ and ATP are involved in TH transport across the plasma membrane (Krenning et al, 1981(Krenning et al, , 1982Centani and Robbins, 1987).…”

mentioning

confidence: 99%

Triiodothyronine Is a High‐Affinity Inhibitor of Amino Acid Transport System L₁ in Cultured Astrocytes

Blondeau

Beslin

Chantoux

et al. 1993

Journal of Neurochemistry

103

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The relationship between the transport of thyroid hormones and that of amino acids was examined by measuring the uptake of amino acids that are characteristic substrates of systems L, A, and N, and the effect of 3,3',5-triiodo-L-thyronine (T3) on this uptake, in cultured astrocytes. Tryptophan and leucine uptakes were rapid, Na(+)-independent, and efficiently inhibited by T3 (half-inhibition at approximately 2 microM). Two Na(+)-independent L-like systems (L1 and L2), common to leucine and aromatic amino acids, were characterized kinetically. System L2 had a low affinity for leucine and tryptophan (Km = 0.3-0.9 mM). The high-affinity system L1 (Km approximately 10 microM for both amino acids) was competitively inhibited by T3 with a Ki of 2-3 microM (close to the T3 transport Km). Several T3 analogues inhibited system L1 and the T3 transport system similarly. Glutamine uptake and alpha-(methylamino)isobutyric acid uptake were, respectively, two and 200 times lower than tryptophan and leucine uptakes. T3 had little effect on the uptakes of glutamine and alpha -(methylamino)isobutyric acid. The results indicate that the T3 transport system and system L1 are related.

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“…It was previously shown that the Km of the T3 transport system of rat hepatocytes showed a homoge¬ neous temperature dependence between 0 and 37°C (11,14). The medium was removed and transport exper¬ iments were started by the rapid addition of 0.3 ml…”

Section: Pre-equilibration Of Washed Erythrocytes With [123i]t3mentioning

confidence: 99%

Erythrocyte-associated triiodothyronine in the rat: a source of hormone for target cells

Francon

Osty

Chantoux

et al. 1990

Acta Endocrinologica

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The accumulation of T3 by rat erythrocytes and its transfer to cultured rat hepatocytes were investigated. The amount of erythrocyte-associated T3 in whole rat blood was determined at 37\s=deg\C.The ratio of erythrocyte-associated T3 to plasma total T3 was 0.235 over a wide range of T3 concentrations, i.e. there is 25 times as much T3 in the erythrocyte compartment as free in the plasma. Influx and efflux of T3, which were shown previously to be carrier-mediated, proceeded rapidly (t\m=1/2\ \ m=appr ox\ 12-15 sec at 25\s=deg\C). These results suggest that erythrocytes are involved in the supply of T3 to target cells. This was checked by studying [125I]T3 uptake by cultured rat hepatocytes incubated either with erythrocyte suspensions pre-equilibrated with labelled T3 or with extracellular medium from the same erythrocyte suspensions. In protein-free medium, the initial velocity of T3 uptake was 1.5-fold faster in the presence of the erythrocyte suspension. Uptake was saturable, the apparent Km of T3 uptake (nmol/l) was 163\m=+-\13in the absence of erythrocytes and 102\m=+-\6in their presence. Vmax (fmol \ m=. \ min\m=-\1\ m=. \ wel l \m=-\1) was similar in both cases (477 \m=+-\26 and 511 \m=+-\20, respectively). In the presence of diluted plasma (1:16 dilution) and in the presence of the erythrocyte suspension, a 2-fold increase of initial velocity was obtained. Plasma by itself increased (4-5 times) the initial velocity of uptake. The time-courses and kinetic constants of T3 binding to hepatocyte nuclear receptors were similar whether hepatocytes were incubated with or without erythrocytes. These results show that part of the erythrocyte-associated T3 adds to the free pool of hormone and can thus be considered as a biologically active compartment, suggesting that rat erythrocytes may serve as a blood-carrier for T3.Thyroid hormones are transported to their target cells by the blood stream, bound to serum binding proteins. Only a small fraction of thyroid hor¬ mones is free. It is currently believed that the plasma free fraction is the source of thyroid hor¬ mones delivered to the tissues, although the role of the protein-bound thyroid hormones (mainly the albumin-bound fraction) is a question under debate (1-4). j Uptake of thyroid hormones by human erythro¬ cytes has been known for over 30 years (5). Re¬ cently, the iodothyronine content of human eryth¬ rocytes was measured in thyroid diseases (6,7). The role of erythrocytes as a potential source of thyroid hormones in the microcirculation of target tissues has not been explored. We have recently shown (8) that T3 crosses the plasma membrane of rat eryth¬ rocytes via a saturable carrier-mediated transport system. At 37°C, the influx and efflux of T3 are very rapid (t'A = 3 sec). We reported evidence that T, is trapped intracellularly rather than bound at the external cell surface. T4 uptake, in contrast, is not carrier-mediated, but occurs by a slow process of free diffusion (8). These observations suggest that rat erythrocytes play a role in the inter-organ t...

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Uptake of L-triiodothyronine into human cultured lymphocytes

Cited by 41 publications

References 12 publications

Role of sodium in thyroid hormone uptake by rat skeletal muscle.

Role of sodium in thyroid hormone uptake by rat skeletal muscle.

Triiodothyronine Is a High‐Affinity Inhibitor of Amino Acid Transport System L₁ in Cultured Astrocytes

Erythrocyte-associated triiodothyronine in the rat: a source of hormone for target cells

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Uptake of L-triiodothyronine into human cultured lymphocytes

Cited by 41 publications

References 12 publications

Role of sodium in thyroid hormone uptake by rat skeletal muscle.

Role of sodium in thyroid hormone uptake by rat skeletal muscle.

Triiodothyronine Is a High‐Affinity Inhibitor of Amino Acid Transport System L1 in Cultured Astrocytes

Erythrocyte-associated triiodothyronine in the rat: a source of hormone for target cells

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Triiodothyronine Is a High‐Affinity Inhibitor of Amino Acid Transport System L₁ in Cultured Astrocytes