High-performance liquid chromatographic separation of iodoamino acids for tracer turnover studies of thyroid hormones in vivo

Bianchi, R.; Molea, N; Cazzuola, F.; Fusani, L.; M, Lotti; Bertelli, Paolo; Ferdeghini, M; Mariani, Giuliano

doi:10.1016/s0021-9673(01)89060-9

Cited by 12 publications

(3 citation statements)

References 19 publications

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“…Briefly, chomatography was performed by a 10-m C18 silica gel column (3 ϫ 300 mm); mobile phase was methanol-water (55:45) with a flow rate of 1.2 ml/min at a pressure of 2,800 psi (2). Radiolabeled T4 and T3 were added to measure recovery and to identify the iodothyronine of interest (i.e., T4 and T3) after extraction and HPLC separation.…”

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confidence: 99%

Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation

Colantuoni¹,

Marchiafava²,

Lapi³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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The aim of the present study was to assess the effects of topically applied triiodothyronine (T3) and thyroxine (T 4 ) on the arterioles of hamster cheek pouch microcirculation in vivo. Microvessels were visualized using a fluorescent microscopy technique. Topical application of T3 (3.08, 30.8, 61.5, 307, 615, and 6,150 nM/l) consistently induced dose-dependent dilation of arterioles within 2.0 Ϯ 0.5 min of administration. The application of T4 (150, 257, 514, and 5,140 nM/l) caused different dose-dependent effects: dilation at the three lower doses within 16 Ϯ 2 min and rhythmic diameter changes at the highest dose. Aging of hamsters did not alter the arteriolar responses to T3 and T4. T3-induced dilation was countered by the inhibition of nitric oxide synthase with N G -nitro-Larginine-methyl ester or N G -nitro-L-arginine. Iopanoic acid (IPA), which inhibits types I and II 5Ј-deiodinase, abolished the dilation elicited by 514 nM T4 but did not affect T3-dependent dilation. 6-Propyl-2-thiouracil (PTU), which inhibits type I 5Ј-deiodinase only, did not affect the dilation induced by T4. IPA and PTU did not impair arteriolar dilation induced by acetylcholine or sodium nitroprusside. These results indicate that T3 induces arteriolar dilation, likely through nitric oxide release. The local conversion of T4 to T3 appears to be crucial for the dilation induced by T4. microcirculation; vasodilation; arterioles; nitric oxide; N G -nitro-Larginine methyl ester; N G -nitro-L-arginine; iopanoic acid; 6-propyl-2-thiouracil; thyroid hormones THE THYROID GLAND synthesizes and releases the thyroid hormones (THs) mainly as tetraiodothyronine (thyroxine, T 4 ) (15). Most of the biologically active triiodothyronine (T 3 ) derives from the conversion of T 4 by 5Ј monodeiodination (types I and II 5Ј-deiodinase) in peripheral tissues (17,19). Type I 5Ј-deiodinase has a primary role in maintaining circulating T 3 levels, whereas type II 5Ј-deiodinase regulates the intracellular concentration of T 3 (12, 18). The direct effects of the THs are triggered by their binding to nuclear receptors (3). Recently, T 3 and T 4 have been shown to stimulate extranuclear sites. A number of nongenomic effects of T 3 have also been identified, including ion fluxes at the level of the plasma membrane (11).Both THs markedly affect the peripheral vascular tone (10). However, the mechanisms by which they influence the peripheral vasculature have not been fully explained. Their vasodilating effects have been related to the local formation of vasodilatory substances due to metabolic activity, oxygen consumption, and heat production. Furthermore, it has been shown that both THs directly interact with vascular smooth muscle (VSM) cells of isolated rabbit mesenteric artery, causing dilation; in particular, T 4 has a greater inhibitory effect than T 3 on VSM contraction (9). In vitro studies have also demonstrated that exposure to T 3 of VSM cells isolated from the rat aorta caused these cells to relax rapidly. T 4 did not compete for the binding sites of ...

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Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation

Colantuoni¹,

Marchiafava²,

Lapi³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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“…Additional studies on thyroid hormone metabolism have been carried out, such as triiodothyronine uptake kinetics measurements in animal erythrocytes', and rate of receptor uptake obtained using tracer-labeled hormone 2 .…”

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confidence: 99%

Thyroxine Hair Content in Congenital Hypothyroidism and Hyperthyroidism

Zamboni¹,

Camilot²,

Francia³

et al. 2003

Journal of Pediatric Endocrinology and Metabolism

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Using the determination of thyroxine (T4) hair content, we studied 16 hypothyroid newborns diagnosed by means of our regional screening program, and five hypothyroid infants, undetected at birth, at diagnosis and after 3 months of substitutive therapy (8-10 microg/kg/day L-thyroxine in newborns; 15 microg/kg/day in infants), and 13 hyperthyroid adults. Hair T4 content was similar at diagnosis in hypothyroid newborns (2.6 +/- 2.3 pg/mg hair) and in infants undetected at birth (2.4 +/- 1.7 microg/mg hair), but very high only in the latter after therapy (23.2 +/- 3.9 microg/mg hair). Untreated hyperthyroid adults surprisingly evidenced lower hair T4 (0.4 +/- 0.2 microg/mg hair) than controls (1.5 +/- 0.3 microg/mg hair). We suggest these findings are due to differential tissue storage of thyroid hormone, related to the different blood T4 concentration. Therefore, T4 hair assay could be a non-invasive method to further assess thyroid status.

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“…To elucidate contamination of rT3 with T3 or T4, the purity of rT3 was studied using high performance liquid chromatography (HPLC) according to the method of Bianchi et al (1984) with slight modification. In short, T4, T3 and rT3 were injected to µ C-18 column (3.9 x 300 mm) (Waters Nihon Waters Ltd, Tokyo, Japan).…”

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3,3′,5′-Triiodothyronine inhibits ontogenetic development of iodothyronine-5′-deiodinase in the liver of the neonatal mouse

Han

Sato²,

Fujii³

et al. 1988

Acta Endocrinologica

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To elucidate the effect of rT3 on iodothyronine-5\m='\-deiodinatingactivity (I-5\m='\-DA) in the liver of neonatal mice, rT3 was injected sc on the 5\p=n-\8thday after birth and I-5\m='\-DAin the liver was determined. A single injection of rT3 (0.01\p=n-\1\g=m\g/g) inhibited the ontogenetically developing I-5\m='\-DAin a dose-and ti me\x=req-\ dependent manner. The inhibitory effect was reversible and specific for I-5\m='\-DA.Lineweaver-Burk analysis revealed that the time-and dose-dependent decrease in the enzyme activity was due to a decrease in Vmax with no alteration in Km values (5 \m=x\ 10\m=-\8 mol/l). The maximal inhibitory effect was observed at a dose of 1 \g=m\grT3/g, whereas the inhibitory effect was diminished at greater doses (4\p=n-\10\g=m\g/g),probably owing to a contamination with T4 of the rT3 preparation administered. Furthermore, consistent with our previous in vitro findings, rT3 inhibited the I-5\m='\-DAinduced by T3 in the liver of neonatal mice. These findings suggest that rT3 inhibited I-5\m='\-DA in the liver of neonatal mice by decreasing the amount of enzyme available to the substrate and that rT3 also elicited an antagonistic effect against T3 in the induction of I-5\m='\-DAin vivo.

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High-performance liquid chromatographic separation of iodoamino acids for tracer turnover studies of thyroid hormones in vivo

Cited by 12 publications

References 19 publications

Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation

Effects of tetraiodothyronine and triiodothyronine on hamster cheek pouch microcirculation

Thyroxine Hair Content in Congenital Hypothyroidism and Hyperthyroidism

3,3′,5′-Triiodothyronine inhibits ontogenetic development of iodothyronine-5′-deiodinase in the liver of the neonatal mouse

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