CHANGES IN PLASMA-CONCENTRATIONS OF GONADOTROPINS AND STEROID-HORMONES DURING THE FORMATION OF BOVINE FOLLICULAR CYSTS INDUCED BY THE ADMINISTRATION OF ACTH

Bovine follicular cysts were induced by treatments with ACTH (3 mg, im ) daily for 14 days beginning in the late luteal phase. Cortisol conce ntrations in plasma significantly increased after ACTH treatments. Dur ing the formation of follicular cysts induced by the injections of ACT H, mean plasma concentrations of progesterone were significantly highe r than those in the untreated preovulatory period, while mean plasma c oncentrations of estradiol-17 beta were significantly lower. During th e treatment period, mean plasma concentrations of LH and FSH remained low, and the preovulatory surges of LH and FSH did not occur. Suppress ed concentrations of LH and FSH might be caused by the increases in se cretions of cortisol and progesterone, and by the decrease in secretio n of estradiol-17 beta.