STUDIES ON THE THYROID STIMULATING HORMONE-ACTIVATED NA+K+-ATPASE AND IODIDE TRANSPORTER IN CULTURED RAT-THYROID CELLS AND THE EFFECTS OF DRUGS

Exposure of rat thyroid FRTL-5 cells to high concentrations of thyroid stimulating hormone (TSH) for 24 hr in vitro activated 125iodide but not ouabain-sensitive 86Rb transport in the cells, whereas after 27 hr and above there were significant increases in the activity of both transporters. This was similar to results obtained in propylthiouracil-treated rats in vivo where, unlike the early reported increases in iodide transport, activation of thyroidal Na+K+-ATPase activity in thyroid membranes occurred around 24-48 hr following rises in serum TSH. These data confirm the presence of a Na+K+-ATPase in cultured rat FRTL-5 thyroid cells, which is activated several hours later than iodide accumulation by TSH stimulation. This pump is sensitive to the cardiac glycoside ouabain as well as other agents affecting intracellular Na+ ion concentrations such as monensin and amiloride. © 1990.