CHANGES IN PITUITARY SOMATOTROPHS AND LACTOTROPHS ASSOCIATED WITH OVARIAN REGRESSION IN THE TURKEY HEN (MELEAGRIS-GALLOPAVO)

Hyperprolactinemia has been associated with incubation behavior and ov arian regression in turkey hens, Preliminary data show that tamoxifen, a partial estradiol receptor antagonist, may effect ovarian regressio n, The objectives of the study were to induce ovarian regression in eg g-laying turkey hens by administration of tamoxifen, to determine whet her incubation behavior would be effected by tamoxifen treatment and t o examine the distribution of lactotrophs and somatotrophs and their i mmunocytochemical changes in the adenohypophysis due to a change in re productive state, Two commercial strains of turkey hens mere administe red tamoxifen (experimentals) or vehicle (controls) intramuscularly (4 0 mg/hen/d). Equal numbers of experimental and control hens were kille d for sample collection after 5, 9 and 14 days (n = 4 per strain) of t reatment, Blood samples were collected for hormone assay and pituitari es prepared for immunocytochemistry. Tamoxifen treatment for 9 and 14 days induced ovarian regression but not incubation behavior, Plasma lu teinizing hormone levels were significantly increased after 5 and 9 da ys of tamoxifen administration, whereas prolactin and growth hormone l evels were unchanged, Somatotrophs were found predominantly in the cau dal portion and lactotrophs occurred in the cephalic lobe of the pitui tary. Relative to controls, the prolactin immunoreactive area was sign ificantly greater in tamoxifen-treated hens, whereas the growth hormon e immunoreactive area was reduced.