CHANGES IN THE LEVELS OF LUTEINIZING HORMONE IN THE PITUITARY OF THE DOMESTIC FOWL DURING AN OVULATORY CYCLE

Abstract

SUMMARY The quantities of luteinizing hormone (LH) in the pituitary glands of the domestic fowl have been measured during an ovulatory cycle using the method of ovarian ascorbic acid depletion. Extracts of avian anterior pituitary were qualitatively similar to a standard preparation of HCG in this test and the activity was destroyed by treatment with urea. During the ovulatory cycle the levels of LH in the pituitary underwent two major changes, being high at the point of ovulation, falling and remaining low for 6 hr. after ovulation and then rising to a second peak 8 hr. before the next ovulation. The levels decreased rapidly and remained low until at least 2 hr. before ovulation. It is suggested that the variations in pituitary LH content are the result of suppression of release by ovarian hormones produced by the maturing follicles.