Kinetics of Distribution of Radioactive Perchlorate in Rat and Guinea-Pig Thyroid Glands

Abstract

SUMMARY The thyroidal uptake of 36ClO4− and the effect of stable perchlorate ion and functional state of the thyroid, such as after long-term administration of propylthiouracil (PTU) or after hypophysectomy, on the uptake of 36ClO4− were studied in rats and guinea-pigs. Based on the analysis of uptake curves, radioactive inulin and sulphate spaces, and histological measurements of compartmental sizes of the thyroid, the relative concentrations of 36ClO4− in the various compartments were calculated and compared with those of 36Cl-. The passage of 36ClO4− and 36Cl− across both the basal and the apical membranes of the follicular cells in the different conditions were analysed. The results suggest that 36ClO4− is concentrated in the lumen of the thyroid by a two-step process. It is actively transported across the basal cell membrane from the interstitial fluid into follicular cells, and is further concentrated in passage across the apical membrane into the lumen. The evidence suggests that the latter process is also an active one.

Thyroid-stimulating hormone increases active transport of perchlorate into thyroid cells

“…This is in contradiction to previous studies showing that radiolabeled perchlorate was concentrated in thyroid tissue in vivo (9,10,32) and contrasts with the selectivity series based on physiological anion transport in thyroid tissue: , 34, 35). Recently, Dohan et al (14) published additional evidence of NIS-mediated active transport of perchlorate both in vivo and in vitro.…”

Evidence for Competitive Inhibition of Iodide Uptake by Perchlorate and Translocation of Perchlorate into the Thyroid

“…Similar to the uptake data of Chow and Woodbury (1970), newly available data from our laboratory (Yu et al 2002) showed two distinct phases in the clearance of 36 ClO − 4 from the male rat thyroid after an IV dose. The first phase shows quick elimination, presumably diffusion from the follicle; the second phase is slower, suggesting slow release from a deep compartment (the lumen).…”

The Na + /I − symporter (NIS) mediates electroneutral active transport of the environmental pollutant perchlorate

“…Indeed, ClO 4 Ϫ inhibition is one of the clearest hallmarks of NIS-mediated I Ϫ transport in both the thyroid and other tissues. Mechanistically, however, to date it has remained uncertain whether ClO 4 Ϫ is a NIS blocker or a transported substrate of NIS (2,(10)(11)(12)(13)(14).…”