Previous studies (2) indicated that a (probably indirect) relationship existed between thyroidal ouabain-sensitive adenosine triphosphatase (ATPase) activity and iodide transport; they were also compatible with the idea that the known stimulating effect of thyrotropin (TSH) on the thyroidal iodide pump may be mediated by activation of ouabain-sensitive ATPase. In the thyroids of 23 normal rats fed Purina Laboratory Chow, ouabain-sensitive ATPase activity was found to be 70 ± 3 (SE) pmoles inorganic phosphate (Pi) per g wet tissue per hr, or 6 % of that of total ATPase. The thyroid serum l'adioiodide concentration ratio (T/S) in 12 of these rats averaged 44. Factors which increased the output of endogenous TSH [1% NaC104 in the drinking water, low iodine intake, injections of propylthiouracil (PTU)] raised the activity of thyroidal ouabain-sensitive ATPase, both in absolute terms (up to over 500 μmoles Pi per g per hr) and as the percentage of that of total ATPase (up to 20% or more). Except for the NaClO4- treatment, the regimens elevated the T/S in a roughly parallel fashion (up to over 200). However, when thyroidal ouabain-sensitive ATPase activity was plotted against T/S in rats given no PTU or injected with 20 mg/day for 1, 2 or 3 days, the correlation was poor. Depression of the T/S (to 0.5-5) by chronic triiodothyronine- treatment or hypophysectomy was not accompanied by a consistent change in the ouabain-sensitive ATPase activity of the thyroid. When the T/S of hypophysectomized rats was raised with TSH +PTU given for 1 or 3 days (by factors ranging from over 10 to over 100), thyroidal ouabain-sensitive ATPase activity either increased only slightly or even decreased. The results do not preclude the possibility that a basal level of ouabain-sensitive ATPase activity is a prerequisite for iodide transport in the rat thyroid, but they show that stimulation of the thyroidal iodide pump by TSH is not secondary to an over-all increase of ouabain-sensitive ATPase action in the gland.(Endocrinology79: 801, 1966)
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Brunberg et al. (1966) studied this question.