Changes in pituitary somatotrophs and lactotrophs associated with ovarian regression in the turkey hen (Meleagris gallopavo).
Hyperprolactinemia has been associated with incubation behavior and ovarian regression in turkey hens. Preliminary data show that tamoxifen, a partial estradiol receptor antagonist, may effect ovarian regression. The objectives of the study were to induce ovarian regression in egg-laying turkey hens by administration of tamoxifen, to determine whether incubation behavior would be effected by tamoxifen treatment and to examine the distribution of lactotrophs and somatotrophs and their immunocytochemical changes in the adenohypophysis due to a change in reproductive state. Two commercial strains of turkey hens were administered tamoxifen (experimentals) or vehicle (controls) intramuscularly (40 mg/hen/d). Equal numbers of experimental and control hens were killed for sample collection after 5, 9 and 14 days (n = 4 per strain) of treatment. Blood samples were collected for hormone assay and pituitaries prepared for immunocytochemistry. Tamoxifen treatment for 9 and 14 days induced ovarian regression but not incubation behavior. Plasma luteinzing hormone levels were significantly increased after 5 and 9 days of tamoxifen administration, whereas prolactin and growth hormone levels were unchanged. Somatotrophs were found predominantly in the caudal portion and lactotrophs occurred in the cephalic lobe of the pituitary. Relative to controls, the prolactin immunoreactive area was significantly greater in tamoxifen-treated hens, whereas the growth hormone immunoreactive area was reduced.
Ramesh
R
R
Department of Poultry Science, University of Maryland, College Park 20742, USA.
Proudman
J A
JA
Kuenzel
W J
WJ
D000818:Animals; D002452:Cell Count; D004965:Estrogen Antagonists / Q000633:toxicity; D005260:Female; D005298:Fertility / Q000187:drug effects; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000097:blood / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D010049:Ovarian Diseases / Q000139:chemically induced*; D006080:Ovarian Follicle / Q000187:drug effects; D010053:Ovary / Q000187:drug effects*; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000187:drug effects / Q000473:pathology; D013629:Tamoxifen / Q000633:toxicity; D014422:Turkeys / Q000502:physiology*
D004965:Estrogen Antagonists; D013629:Tamoxifen; D007986:Luteinizing Hormone