Interrelationship between insulin-like growth factor I-induced activation of the Na+/H(+)-antiporter and intracellular Ca(2+)-mobilization in thyroid cells. |
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Authors: | N Takasu I Komiya Y Nagasawa T Asawa Y Shimizu T Yamada |
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Institution: | Department of Gerontology, Endocrinology and Metabolism, School of Medicine, Shinshu University, Nagano-ken, Japan. |
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Abstract: | Insulin-like growth factor I (IGF-I) increased cytoplamic pH (pHi) and cytoplasmic Ca2+ ( Ca2+]i) in cultured porcine thyroid cells. Inhibition of the Na+/H(+)-antiporter by dimethylamiloride or a reduction of external Na(+)-concentrations attenuates the increases in pHi and Ca2+]i. The Ca2+]i response to IGF-I is a pHi-dependent process. IGF-I activates Na+/H(+)-antiporter and alkalinizes thyroid cells. The resulting increase in pHi facilitates the Ca2+]i response by adjusting the pHi closer to the pHi-optimum of the intracellular Ca(2+)-mobilizing system. One of the biological functions of IGF-I-induced activation of the Na+/H(+)-antiporter is to shift the pHi to an optimal value for the Ca2+]i response. |
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