Thyroid Na+/I− Symporter

Eskandari, Sepehr; Loo, Donald D. F.; Dai, Ge; Levy, Orlie; Wright, Ernest M.; Carrasco, Nancy

doi:10.1074/jbc.272.43.27230

Cited by 416 publications

(180 citation statements)

References 34 publications

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“…; different letters indicate statistically significant differences. Eskandari et al 1997). In our study, exercise had no effect on TPO and the NIS function.…”

Section: Discussionmentioning

confidence: 67%

The effect of acute exercise session on thyroid hormone economy in rats

Fortunato

Ignacio²,

Padrón³

et al. 2008

Journal of Endocrinology

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The hypothalamic-pituitary-thyroid axis is affected by acute exercise, but the mechanisms underlying thyroid function changes after exercise remain to be defined. The aim of this study was to elucidate the effects of a session of acute exercise on the treadmill at 75% of maximum oxygen consumption on thyroid function of rats. Male Wistar rats were divided into five groups: control (without exercise), and killed immediately after (0 min) or 30, 60, and 120 min after the end of the exercise session. A significant increase in serum tri-iodothyronine (T 3 ) occurred immediately after the exercise, with a gradual decrease thereafter, so that 120 min after the end of the exercise, serum T 3 was significantly lower than that in controls. Total thyroxine (T 4 ) increased progressively reaching values significantly higher than that in the control group at 120 min. T 3 /T 4 ratio was significantly decreased 60 and 120 min after the exercise, indicating impaired T 4 -to-T 3 conversion. Liver type 1 deiodinase activity (D1) significantly decreased at 60 and 120 min, while pituitary D1 increased progressively from 30 to 120 min after the exercise, and thyroid D1 was increased only immediately after the end of the exercise. Brown adipose tissue (BAT) type 2 deiodinase activity (D2) was significantly lower at 30 min, but pituitary D2 remained unchanged. No change in serum thyrotropin was detected, while serum corticosterone was significantly higher 30 min after the exercise. Our results demonstrate that decreased liver D1 and BAT D2 might be involved in the decreased T 4 -to-T 3 conversion detected after an exercise session on the treadmill.

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“…; different letters indicate statistically significant differences. Eskandari et al 1997). In our study, exercise had no effect on TPO and the NIS function.…”

Section: Discussionmentioning

confidence: 67%

The effect of acute exercise session on thyroid hormone economy in rats

Fortunato

Ignacio²,

Padrón³

et al. 2008

Journal of Endocrinology

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“…These data indicate that decreases in current were partly due to decreased proton concentrations at the immediate proximity of the extracellular membrane. Decreases in current during perfusion may be due to intracellular substrate or H ϩ accumulation (trans-inhibition), in analogy to observations for other transporters (34,35). None of these factors are expected to compromise the accuracy of stoichiometry determination.…”

Section: Table I Apparent Affinity Constants For a Variety Of Dipeptidesmentioning

confidence: 99%

Stoichiometry and Kinetics of the High-affinity H+-coupled Peptide Transporter PepT2

Chen¹,

Zhu²,

Smith³

et al. 1999

Journal of Biological Chemistry

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Proton-coupled peptide transporters mediate the absorption of a large variety of di-and tripeptides as well as peptide-like pharmacologically active compounds. We report a kinetic analysis of the rat kidney highaffinity peptide transporter PepT2 expressed in Xenopus oocytes. By use of simultaneous radioactive uptake and current measurements under voltage-clamp condition, the charge to substrate uptake ratio was found to be close to 2 for both D-Phe-L-Ala and D-Phe-L-Glu, indicating that the H ؉ :substrate stoichiometry is 2:1 and 3:1 for neutral and anionic dipeptides, respectively. The higher stoichiometry for anionic peptides suggests that they are transported in the protonated form. For D-Phe-L-Lys, the charge:uptake ratio averaged 2.4 from pooled experiments, suggesting that Phe-Lys crosses the membrane via PepT2 either in its deprotonated (neutral) or its positively charged form, averaging a H ؉ :Phe-Lys stoichiometry of 1.4:1. These findings led to the overall conclusion that PepT2 couples transport of one peptide molecule to two H ؉ . This is in contrast to the low-affinity transporter PepT1 that couples transport of one peptide to one H ؉ . Quinapril inhibited PepT2-mediated currents in presence or in absence of external substrates. Oocytes expressing PepT2 exhibited quinapril-sensitive outward currents. In the absence of external substrate, a quinapril-sensitive proton inward current (proton leak) was also observed which, together with the observed pH-dependent PepT2-specific presteady-state currents (I pss ), indicates that at least one H ؉ binds to the transporter prior to substrate. PepT2 exhibited I pss in response to hyperpolarization at pH 6.5-8.0. However, contrary to previous observations on various transporters, 1) no significant currents were observed corresponding to voltage jumps returning from hyperpolarization, and 2) at reduced extracellular pH, no significant I pss were observed in either direction. Together with observed lower substrate affinities and decreased PepT2-mediated currents at hyperpolarized V m , our data are consistent with the concept that hyperpolarization exerts inactivation effects on the transporter which are enhanced by low pH. Our studies revealed distinct properties of PepT2, compared with PepT1 and other ion-coupled transporters.In kidney and intestine, enzymatic degradation of proteins and peptides produces oligopeptides that are absorbed across the brush-border membrane of epithelial cells, followed by breakdown into free amino acids (1-3). The absorption is carried out by proton-driven cotransport systems, as demonstrated by studies using brush-border membrane vesicles, epithelial cells in culture, intact epithelial tubules, and recombined peptide transporters (4 -10). A large variety of diand tripeptides, as well as pharmacologically active peptidelike compounds such as ␤-lactam antibiotics and angiotensinconverting enzyme inhibitors, are transported (11-13). Peptide transporters have been cloned since 1994 (3, 14 -19) and were shown to accept many oligopeptide...

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“…Más del 90% es absorbido durante los primeros 60 min. Se distribuye en la sangre como un ion extracelular, similar al cloruro, para incorporarse a las células gracias al cotransportador Na + /I -(NIS) 8 . El NIS es una proteína de la membrana basolateral de la célula folicular que cotransporta dos iones de sodio y un ion yoduro.…”

Section: Biologíaunclassified

La medicina nuclear y el cáncer diferenciado de tiroides

Medina-Ornelas¹,

García-Pérez²,

Granados-García³

2022

GAMO

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Gaceta Mexicana de Oncologia. 2017;16(4):239-248 resumen: Los afectados por cáncer diferenciado de tiroides (CDT) suelen tener un curso clí-nico favorable, pero algunos pueden mostrar un curso agresivo con recaídas. El tratamiento óptimo aún es controvertido, en especial respecto a la extensión de la cirugía, las indicaciones de radioyodo y la supresión de hormona estimuladora del tiroides (TSH). La evaluación correcta de los riesgos facilita un enfoque selectivo de la terapia. Presentamos una revisión del papel de la medicina nuclear en la evaluación, tratamiento y seguimiento de pacientes afectados por esta interesante enfermedad. (creativecommons.org/licenses/by-nc-nd/4.0/). abstract Those affected by differentiated thyroid cancer tend to have a favorable clinical course, but some may show an aggressive course with relapses. The optimal treatment is still controversial, especially regarding the extent of surgery, indications for radioiodine and suppression of thyroid-stimulating hormone. Correct risk assessment facilitates a selective approach to therapy. We present a review of the role of nuclear medicine in the evaluation, treatment and follow-up of patients affected by this interesting disease. PalaBraS ClaVECáncer de tiroides; Radioyodo; Medicina nuclear; Tratamiento KEY WorDSThyroid cancer; Radioiodine; Nuclear medicine; Treatment introDuCCión Según Globocan, en 2012 en México ocurrieron 3,036 casos de cáncer de tiroides (725 en hombres y 2,311 en mujeres), que constituyeron el 2.1% del total de neoplasias malignas 1 . El CDT representa al menos el 85% de los casos e incluye los tipos papilar, folicular y de células de Hürtle. El cáncer papilar, el tipo más frecuente, se asocia a una excelente supervivencia, pero algunos pacientes tienen un curso clínico menos favorable, con metástasis o recaídas que afectan a los ganglios linfáticos cervicales y, con menor frecuencia, a los pulmones y el hueso 2,3 . La medicina nuclear se sirve de las peculiaridades de la fisiopatología del CDT y juega un papel muy importante tanto en el tratamiento adyuvante como en el seguimiento y manejo de las recaídas. El tratamiento debe ser el más eficaz posible, con las menores secuelas y el menor costo; por ello se enfatiza el tratamiento individualizado, acorde al tipo histológico, la extensión de la enfermedad y el riesgo de recaída. YoDo 131El yodo 131 ([131]I o radioyodo) es producido en un reactor nuclear mediante la irradiación neutrónica de dióxido de telurio durante la fisión del uranio. Su vida media física es de 8.02 días. Los átomos del yodo 131 emiten partículas β con

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Thyroid Na+/I− Symporter

Cited by 416 publications

References 34 publications

The effect of acute exercise session on thyroid hormone economy in rats

The effect of acute exercise session on thyroid hormone economy in rats

Stoichiometry and Kinetics of the High-affinity H+-coupled Peptide Transporter PepT2

La medicina nuclear y el cáncer diferenciado de tiroides

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