Transport of free 211At and 125I- in thyroid epithelial cells: effects of anion channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid on apical efflux and cellular retention.
BACKGROUND
Astatine ((211)At; alpha-emitter; t(1/2)=7.21 h) shares several features with its halogen neighbour iodine. In the present study, we investigated whether 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) can be used to increase the cellular retention time of (211)At and radioiodide in thyroid epithelial cells.


METHODS
The transepithelial transport and cellular uptake of (211)At and (125)I(-) were studied simultaneously in porcine thyrocytes cultured in bicameral chambers. The cells were prestimulated with thyroid-stimulating hormone (TSH) or epidermal growth factor (EGF) for 48 h. In addition, the acute effects of DIDS and forskolin were investigated.


RESULTS
The transepithelial transport of both radionuclides was stimulated by TSH and down-regulated by EGF. DIDS rapidly reduced the efflux and increased the cellular content of (125)I(-) in control and TSH-stimulated cells, whereas DIDS had no effect on (125)I(-) transport in EGF-treated cells. DIDS blocked the (211)At efflux only in TSH-stimulated cells. Unexpectedly, DIDS caused an accelerated efflux of (211)At in both control and EGF-stimulated cells and, furthermore, reduced the cellular content of (211)At in the EGF-stimulated cultures. DIDS had no effect on the forskolin-induced efflux of the two radionuclides.


CONCLUSIONS
The magnitude of thyroidal (211)At uptake and efflux is similar to that of (125)I(-), strongly dependent on the functional activity of the cells. However, (211)At efflux likely involves several permeating mechanisms with different sensitivity to DIDS, which are at least partly not shared by (125)I(-). The results suggest that anion channel blockage is potentially useful to increase the absorbed dose from both (211)At and radioiodine in NIS-expressing tumours.
Lindencrona
Ulrika
U
Department of Radiation Physics, Göteborg University, SE-413 45 Göteborg, Sweden. ulrika.lindencrona@radfys.gu.se
Forssell-Aronsson
Eva
E
Nilsson
Mikael
M
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000008:administration & dosage*; D000818:Animals; D017920:Antiporters / Q000037:antagonists & inhibitors; D001246:Astatine / Q000493:pharmacokinetics*; D001693:Biological Transport, Active / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008657:Metabolic Clearance Rate / Q000187:drug effects; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D013552:Swine; D027981:Symporters / Q000037:antagonists & inhibitors*; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000099209:Sodium-Iodide Symporters
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D017920:Antiporters; D001246:Astatine; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D027981:Symporters; D000099209:Sodium-Iodide Symporters