Porcine vasoactive intestinal polypeptide (VIP; 10-9 to 10-7 M) was a potent stimulator of prolactin (PRL) release by anterior pituitary cells from immature and laying turkey hens. Basal and VIP-induced PRL release of cells from laying hens were diminished (P < 0.05) when the cells were cultured for 48 hr in the presence of charcoal-stripped laying hen serum, but not when the cells were cultured in the presence of whole laying hen serum. This change in VIP-induced PRL release was not evident when cells were derived from immature hens. Basal PRL release by cells from laying hens was not altered by the presence of estradiol (E2; 10-12 to 10-5 M), although such release was generally enhanced in cultures of cells from immature hens containing E2. The presence of E2 enhanced (P < 0.05) the magnitude of the VIP-induced PRL release by cultures of cells from laying hens and diminished (P < 0.05) the magnitude of this release in cultures of cells from immature hens. Cells from immature and laying hens exposed to progesterone (P4; 10-5 M) for 96 hr exhibited enhanced basal PRL release, though lower P4 concentrations had no effect. Utilizing cells from laying hens, P4 exposure for 24 hr resulted in diminished (P < 0.05) VIP-induced PRL release, while P4 exposure for 96 hr resulted in markedly enhanced (P < 0.05) VIP-induced PRL release. Basal PRL release was generally not altered by the presence of testosterone (T). The VIP-induced PRL release by cells derived from immature and laying hens was diminished (P < 0.05) by the presence of T. Prolactin release in the turkey is likely modulated by gonadal steroids acting directly on the cells of the anterior pituitary.
Bibliographical noteFunding Information:
i This work was supported by USDA Grant 85 CRCR-1-1838. This is Scientific Journal Series paper 16,177 of the Minnesota Agricultural Experiment Station.