Hydrogen peroxide inhibits iodide influx and enhances iodide efflux in cultured FRTL-5 rat thyroid cells.
This study describes the effects of hydrogen peroxide on the two iodide transport systems, I influx and I efflux, in the cultured FRTL-5 rat thyroid cells. I influx was measured by the amount of I taken up by the cells during incubation with Na125I and NaI for 7 min, and I efflux was measured by calculating the rate of 125I release from the 125I-loaded cells in the presence and absence of 5 mmol/l H2O2. Exposure to greater than 100 mumol/l H2O2 for 40 min caused a significant inhibition of I influx; the inhibition was reversible and non-competitive with iodide. Thyroid Na+K+ ATPase activity, a major mechanism to drive I influx, decreased by 40% after the cells were exposed to 5 mmol/l H2O2 for 10 min. H2O2 enhanced I efflux only when Ca2+ was present in the medium. The mechanism of an enhanced I efflux by H2O2 appears to be mediated through the elevation of free cytosolic Ca2+ concentration. Our data indicate that H2O2 can affect I transport by inhibiting I influx and enhancing I efflux.
Sugawara
M
M
Medical Service, Wadsworth VA Hospital, California.
Yamaguchi
D T
DT
Lee
H Y
HY
Yanagisawa
K
K
Murakami
S
S
Summer
C N
CN
Johnson
D G
DG
Levin
S R
SR
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007454:Iodides / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D013997:Time Factors
D007454:Iodides; D010042:Ouabain; D006861:Hydrogen Peroxide; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium