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  • Title: Extracellular adenosine increases Na+/I- symporter gene expression in rat thyroid FRTL-5 cells.
    Author: Harii N, Endo T, Ohmori M, Onaya T.
    Journal: Mol Cell Endocrinol; 1999 Nov 25; 157(1-2):31-9. PubMed ID: 10619395.
    Abstract:
    We studied the effect of extracellular adenosine on iodide (I-) transport in FRTL-5 thyroid cells. I- accumulation increases after a 48 h exposure to adenosine in a concentration-dependent manner, reaching a maximum of 7.9-fold basal levels at 72 h after the addition of 300 microM adenosine. Neither I- efflux nor intracellular cyclic adenosine monophosphate accumulation is affected by the exposure to adenosine. The stimulation of I- transport by adenosine is partly as a result of an increase in Na+/I- symporter (NIS) mRNA and protein levels. Northern blot analysis revealed that adenosine increases NIS mRNA levels at 24 h, reaching a maximum at 36 h. Western blot analysis demonstrated that adenosine increases NIS protein levels at 36 h, reaching a maximum at 72 h, in parallel with the kinetics of adenosine-induced I- transport. Adenosine increased the promoter activity of a full-length NIS promoter-luciferase chimera, suggesting that the effect of adenosine on NIS mRNA levels is transcriptional. The stimulatory effect of adenosine on NIS mRNA levels, is mimicked by N6-(L-2-phenylisopropyl) adenosine (PIA), an A1 adenosine receptor agonist, and inhibited by 1,3-dipropyl-8-cyclopentylxanthine, an A1 adenosine receptor antagonist, suggesting that the effect is mediated via the A1 adenosine receptor stimulation in FRTL-5 cells. Incubating cells with islet-activating protein inhibited the adenosine-induced NIS mRNA levels. In sum, extracellular adenosine increases NIS gene expression and stimulates I- transport via the A1 adenosine receptor-Gi/Go protein signal transduction pathway.
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