Effect of extracellular sodium on thyroid hormone uptake by mouse thymocytes.
Endocrinology
; 129(4): 2175-9, 1991 Oct.
Article
em En
| MEDLINE
| ID: mdl-1915098
ABSTRACT
In mouse thymocytes, a stereospecific saturable energy-dependent and ouabain-inhibitable system facilitates T3, but not T4, entry. We studied here the effect of sodium depletion on cellular uptake of thyroid hormones by mouse thymocytes. Time-course experiments indicated that extracellular sodium depletion reduced [125I]T3 uptake at each time studied. At equilibrium, the removal of extracellular sodium and its substitution with isoosmotic choline decreased saturable [125I]T3 uptake by 60 +/- 10%; this effect was dose dependent. The substitution of sodium with lithium, instead of choline, had no effect on the uptake process. [125I]T4 uptake was lower than that of [125I]T3 and not affected by sodium depletion. The half-maximal effect of sodium deprivation on [125I]T3 uptake was reached at an extracellular sodium concentration of about 40 mM. The variation of external pH influenced T3 accumulation by thymocytes. [125I]T3 progressively decreased from acid to alkaline pH under normal and sodium-depleted conditions; however, the sodium-dependent fraction was more than doubled at physiological pH compared to that at more acidic and more alkaline pH. The sodium ionophore monensin decreased T3 uptake by 51% at a concentration of 20 microM. These results indicated the existence of a sodium-related mechanism of T3 uptake into mouse thymocytes that does not operate for T4 uptake.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Sódio
/
Timo
/
Tiroxina
/
Tri-Iodotironina
/
Espaço Extracelular
Limite:
Animals
Idioma:
En
Revista:
Endocrinology
Ano de publicação:
1991
Tipo de documento:
Article
País de afiliação:
Itália