INCREASE IN THE FORMATION AND THE SECRETION OF ACTH IN RATS FOLLOWING ADMINISTRATION OF OESTRADIOLMONOBENZOATE

Abstract

The subcut. injn. of 0.25 mg. of alpha-estradiol monobenzoate (1-5 injns. at 10-12 hr. intervals) into normal and adrenaiectomized, Nad-maintained Long-Evans rats of 140-250 g. wt. caused an increase in plasma ACTH of intact rats but none in the already high plasma ACTH of adrenaiectomized animals. ACTH was measured by adrenal ascorbic acid depletion methods. The pituitaries of intact rats became heavier, the concn. of ACTH/mg. gland did not change, and total pituitary ACTH therefore increased after estrogen. In adrenaiectomized rats, pituitary wt. did not change, but the cbncn. of ACTH/mg. pituitary increased, so that total pituitary ACTH was increased. The authors believe the high dose of estrogens they used is a stress which depresses plasma corticoid concn., causing increased ACTH secretion. In adrenaiectomized rats, no further depression of plasma corticoids can occur and no further stimulation of ACTH secretion is possible. Estrogens may also have a direct stimulatory effect on ACTH formation in the pituitary, since the temporary reduction of pituitary ACTH content usually seen immediately after adrenalectomy does not occur in response to estrogen stimulation of increased ACTH secretion.