Plasma concentration of progesterone and estradiol during the ovulatory cycle of the turkey.
Radioimmunoassays were used to estimate concentrations of progesterone and estradiol in the peripheral plasma of hens in relation to the first (C1) or second (C2) ovulation in a sequence. Peak concentrations of progesterone were found at 6--3 hr. before ovulation. There were no consistent changes in estradiol concentrations. When blood samples were taken at 2-hr. intervals for 24--48 hrs., estradiol concentrations peaked at 18 hours before C1 ovulation and during the same time of day (2--6 p.m.) during the period of no ovulation between sequences, but no estradiol peak preceded C2 ovulation. When blood samples were taken from a second population of hens at 1-hr. intervals during the 12 hr. period before expected C2 ovulation, a significant rise in estradiol (P less than 0.01) was associated with the preovulatory peak of progesterone. The preovulatory peak of estradiol in these hens may be linked to a seasonally high rate of secretion of both estradiol and progesterone. As estimated indirectly by hypophysectomy, release of an ovulatory amount of LH in the turkey coincided with the rise of progesterone to the preovulatory peak.
D000818:Animals; D004958:Estradiol / Q000097:blood*; D005260:Female; D007016:Hypophysectomy / Q000662:veterinary; D010060:Ovulation; D011374:Progesterone / Q000097:blood*; D014422:Turkeys / Q000097:blood / Q000502:physiology*
D011374:Progesterone; D004958:Estradiol