Plasma and Follicular Steroid Levels of Laying Hens after the Administration of Gonadotropins

Abstract

Chicken or ovine gonadotropins were injected into laying hens at 12 h after the C₁ oviposition (approximately 14 h before the C₃ ovulation). Plasma and the walls of the 3 largest follicles were taken from the hens within the period from 15-90 min after hormone injection to be assayed for progesterone (P) and estrogen (E) by RIA. P concentrations in plasma and in the 3 largest follicles, particularly the largest one, rose sharply during the first 30 min after the injection of chicken anterior pituitary (CP) or ovine LH (oLH) and reached maximum at 30 min. Plasma and follicular P were sustained at a high level for 90 min after the CP injection, while the P levels in hens given oLH decreased from 45 to 90 min after injection of oLH. CP was effective in causing significant elevation of E in plasma and the 2 smaller follicles. but not in the largest one, at 30 and 45 min after the injection, while no such increase was induced by oLH, excepting in the third follicle, but at only [unknown] time point. The injection of ovine FSH (oFSH), at the highest dose level (400 µg) used, resulted in significant increases of follicular P and plasma E. Synergistic effect between oFSH and oLH was found on P synthesis and release, but not on E. The values of plasma and follicular P elevated by CP and oLH were comparable to those of the preovulatory peak in the normal cycle.