Effects of thyroidectomy, adrenalectomy, thyroid hormones and glucocorticoids on Na+, K+-activated ATP-ase of rat anterior pituitary.

It is well known that the function of the anterior pituitary is controlled by hormones secreted from several peripheral endocrine glands. In the previous reports from this laboratory, TONOUE and YAMAMOTO 14-18) and HOSHINO et al.2, 3) showed that transport and incorporation of amino acids were stimulated in rat anterior pituitary after either thyroidectomy or adrenalectomy. Injection of thyroxine (T4) or glucocorticoids to thyroidectomized or adrenalectomized rats was found to depress the increased transport and incorporation. In vitro addition of these hormones was also highly effective in depressing these two activities. Since Na+, K+-activated ATPase or transport ATPase (tATPase) has been reported to participate in amino acid transport in several tissues 1, 5, 7, 8, 19, 20), it was of interest to investigate changes in pituitary tATPase activity after thyroidectomy, adrenalectomy or administration of thyroid hormones or glucocorticoids in vivo and in vitro. Another purpose of this experiment was to compare the effects of these hormones on tATPase of the anterior pituitary and the thyroid. Thyroidal tATPase was stimulated specifically by estrogens but was not sensitive to either thyroid or adrenocortical hormonesi 12). A part of the present results has been reported preliminarily 13).