Iodine suppression of iodide uptake in FRTL-5 thyroid cells.
Exposure of FRTL-5 cells to iodide (I-) in excess of 3 microM suppresses the concentrative uptake of I-. The depression of I- uptake measured at the steady state is due to decrease in the rate of I- influx and not to an effect on I- efflux. Exposure to NaI is associated with decreased T4 secretion and also depressed Na+-dependent amino acid accumulation. The depression in I- and amino acid transports increases proportionately with the duration of exposure and concentration of I- used but is not associated with alterations in FRTL-5 cell cAMP levels. The I- suppression effect is blocked, however, when methimazole is present during the incubation with NaI. In agreement with studies in vivo, I- suppression in FRTL-5 cells appears to depend on an intermediate in the organification process and to be independent of a TSH-induced cAMP-mediated action.
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D007454:Iodides / Q000378:metabolism* / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D007700:Kinetics; D008713:Methimazole / Q000494:pharmacology; D051381:Rats; D012974:Sodium Iodide / Q000494:pharmacology*; D013954:Thyroglobulin / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism
D000596:Amino Acids; D007454:Iodides; D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D008713:Methimazole; D013972:Thyrotropin; D013954:Thyroglobulin; D000242:Cyclic AMP; D012974:Sodium Iodide; D013974:Thyroxine