Changes in the population of immunoreactive S-100-positive folliculo-stellate cells in hens during induced molting

The goal of this study was to determine whether the population of folliculo-stellate (FS) cells in the hen's pituitary change during induced molting. White Leghorn laying hens were subjected to induced molting by feed withdrawal; feeding was resumed on the fourth day after egg laying ceased. The anterior pituitaries were collected from hens at pretreatment, at 3 and 5 d after feed withdrawal and at 3 d after cessation of egg laying, 10 d after cessation of egg laying (6 d after resumption of feeding), on the day of and 1 wk after resumption of egg laying (RL and 1WRL, respectively). Pituitaries were processed to detect FS cells by immunocytochemistry for the S-100 protein. Sections were then examined under a light microscope with an image analysis computer systern. S-100 immunoreactive cells were found in the cephalic and caudal lobes of the anterior pituitary in all groups of hens. The majority of S-100 immunoreactive cells formed clusters of cells that faced into the follicle and surrounded the glandular cells with long cytoplasmic processes. The S-100 immunoreactive area in the cephalic lobe was significantly increased in the RL group (P < 0.05), but decreased thereafter in 1WRL group. The S-100-positive cell area in the caudal lobe did not show significant changes during induced molting. These results suggest that FS cell population is likely to increase at the final stage of induced molting and may be involved in control of pituitary functions for the resumption of ovulation.