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Title: INCREASED PROLIFERATIVE ACTIVITY AND PROGRAMMED CELLULAR DEATH IN THE TURKEY HEN PITUITARY GLAND FOLLOWING INTERRUPTION OF INCUBATION BEHAVIOR

Author
item RAMESH, R - USDA, ARS, LPSI, GGPL
item KUENZEL, W - UNIVERSITY OF MARYLAND
item Proudman, John

Submitted to: Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Lactotrophs and somatotrophs are the pituitary cells that secrete prolactin (PRL) and growth hormone(GH),respectively. Both PRL and GH regulate growth and reproduction in all animals. Increased secretion of PRL from the pituitary gland is associated with loss of egg production due to expression of incubation behavior or broodiness in the turkey hen. In broody hens, an increase in lactotroph and a reduction in somatotroph population has been reported. Since PRL secretion is decreased precipitously upon interruption of broodiness, this study was conducted to document parallel cellular changes in the pituitary gland. Results showed an increase in somatotrophs and a decrease in lactotrophs, a reversal of cellular change that was noticed at the onset of broodiness. Mammosomatotrophs, the dual GH and PRL secreting cells, were absent in the pituitary gland following interruption of broodiness. Lactotrophs underwent programmed cell death while there was san increased proliferation of pituitary cells which later differentiated t produce GH. This research shows that lactotrophs and somatotrophs undergo reversible cellular changes at different reproductive states. Scientists will use this knowledge to study how to regulate pituitary cell differentiation for improving growth and egg production efficiency in the turkey hens.

Technical Abstract: Interruption of incubation behavior in turkey hens results in a precipitous decline in plasma PRL levels. In order to examine cellular changes in the pituitary gland associated with declining plasma PRL levels, we nest- deprived incubating turkey hens for 0, 1, 2, 3, 4 or 7days. Bromodeoxyuridine (BrdU) was administered to study proliferative activity. Our results suggest that the mid-sagittal pituitary area immunoreactive (ir) to GH was significantly increased while that of PRL was significantly decreased following nest-deprivation for 2 or more days. Terminal deoxy (d)-UTP nick end labeling and PRL-immunostaining revealed an abundance of apoptotic nuclei in the pituitary cephalic and caudal lobes of hens nest- deprived for 2 or more days. Mammosomatotrophs were abundant in hens nest- deprived for 0 days but were absent in hens nest-deprived for 1 or more days. Proliferating (BrdU-ir) cells were significantly abundant in the cephalic and caudal lobes following nest-deprivation for 1 or more days bu were absent in day 0 or in laying hen. Most of the BrdU-ir nuclei in the caudal lobe were not colocalized with GH in hens nest-deprived for 1- 4 days but did colocalize with GH following 7 days of nest-deprivation. In conclusion, nest-deprivation of incubating turkey hens results in(i) programmed cell death of lactotrophs, (ii) disappearance of mammosomatotrophs, (iii) increased proliferative activity of pituitary cells and (iv) recruitment of somatotrophs that arise from mitosis of non- somatotrophic cells and transifferentiation of piuticytes other than lactotrophs.