Changes of immunoreactive inhibin, follicle-stimulating hormone, luteinizing hormone, and progesterone in plasma after short-term food deprivation and during the ovulatory cycle of the domestic hen

The interrelationship between immunoreactive inhibin and follicle-stimulating hormone (FSH) was measured in laying hens after short-term food deprivation and during the ovulatory cycle. Plasma inhibin was estimated by a heterologous radioimmunoassay validated for use in chicken. FSH was measured by a recently developed homologous radioimmunoassay. Ten hens were deprived of food for 10 days (a method to induce artificial moult or to stop egg laying). Blood samples were taken daily via the brachial vein for 10 consecutive days starting on the day of food withdrawal. The data are expressed in relation to the last day of oviposition. Short-term food deprivation, followed by ovarian atrophy, significantly depressed the plasma inhibin and progesterone (P4) concentration. Plasma FSH concentrations significantly increased, while luteinizing hormone (LH) concentrations slightly but not significantly decreased. In another experiment, 6 hens were induced to moult. The control hens (n = 6) were fed ad libitum. On Day 17, the hens were killed and follicular distribution was studied. The atrophy of the large yolky follicles in restricted hens was associated with a significant increase in the number of white follicles. In a third experiment, serial blood samples were taken from hens (n = 15) at 2-hr intervals for 36 hr via a brachial cannula. Plasma immunoreactive inhibin and FSH concentrations did not vary during the ovulatory cycle. LH and P4 increased simultaneously from basal levels to preovulatory peak values 6 hr before ovulation. In conclusion, the inverse relationship between concentrations of FSH and inhibin after induced egg laying stop suggest that, as in mammals, inhibin is important for the inhibition of FSH secretion in the chicken. However, during the ovulatory cycle no such correlation was found.