Changes in Pituitary FSH Concentrations During an Ovulatory Cycle of the Hen

Abstract

IN THE ovary of the hen, several follicles in different stages of development grow simultaneously with the most mature one ovulating. Ovulation usually occurs for a varying number of consecutive days, followed by pauses of 1 or 2 days, and then ovulation resumes. It has been accepted generally that ovulation is induced by an acute release of luteinizing hormone (LH) from the pituitary some 8 hours before ovulation (Fraps, 1955). Recently, it was found that levels of LH content in the pituitary and in the blood fluctuated during the ovulatory cycle of the hen, i.e., two peaks of the LH level appeared in the pituitary (Nelson et al., 1965; Heald et al., 1967; Tanaka and Yoshioka, 1967) and three peaks appeared in the blood (Nelson et al., 1965; Bullock and Nalbandov, 1967). These facts suggest that the release of LH from the pituitary occurs more than once during the ovulatory…