Correlation of iodide transport with Na + ,K+ ATPase, HCO3-ATPase and carbonic anhydrase activities in different functional states of the rat thyroid gland.

The effects of thyrotrophin, hypophysectomy, and chronic treatment with thyroxine and methimazole on radioiodide uptake (thyroid/plasma (T/P) 125I-ratio), protein and DNA contents and activities of Na+, K+-ATPase, HCO-3 ATPase, and carbonic anhydrase (CA) of rat thyroid gland were evaluated. Thyrotrophin given to intact rats slightly increased thyroid iodide uptake, did not affect protein or DNA content, and slightly inhibited CA activity (units/g cell water). Hypophysectomy markedly decreased T/P 125I-ratio, increased protein content, decreased activity of Na+, K+ -ATPase, and slightly increased HCO-3 -ATPase(nmol/mg DNA per min) and CA (units/g cell water) activities. Thyrotrophin given to hypophysectomized rats (as compared with untreated hypophysectomized control animals) markedly increased T/P 125I-ratio, slightly decreased protein content and decreased Na+, K+-ATPase and CA activities. Chronic treatment with methimazole increased T/P 125I-ratio, decreased protein content, markedly increased NA+, K+-ATPase and HCO-3-ATPase activities, and decreased CA activity. Chronic treatment with thyroxine, in contrast, decreased T/P 125I-ratio, decreased Na+, K+-ATPase activity, and increased CA activity. There was a significant inverse correlation between T/P 125I-ratio and CA activity in follicular cells for the various induced functional states of the thyroid.