The objective of this project was to determine the effects of sustained hyperprolactinemia for 7 or 20 d on mammary development in late-pregnant gilts. On day 90 of gestation, gilts were assigned to one of 3 groups to receive intramuscular (IM) injections of (1) canola oil (CTL, n = 18) until day 109 ± 1 of gestation; (2) a dopamine receptor antagonist, domperidone (0.5 mg/kg of body weight [BW]) until day 96 ± 1 of gestation (T7, n = 17); or (3) domperidone (0.5 mg/kg BW) until day 109 ± 1 of gestation (T20, n = 17). Domperidone-treated gilts also received 100 mg of domperidone per os twice daily from days 90 to 93 of gestation. Blood was sampled on days 89, 97, 104, and 110 for prolactin (PRL), insulin-like growth factor 1 (IGF1), lactose, urea, and glucose assays. Mammary glands were collected at necropsy, on day 110, for compositional and cell proliferation analyses. Abundance of mRNA for selected genes was also determined in the mammary gland and the pituitary gland. On day 97 of gestation, PRL concentrations were 3 times greater for T20 and T7 than CTL gilts and were also greater for T20 than T7 and CTL gilts on days 104 and 110 (P < 0.001). Concentrations of IGF1 in T20 and T7 gilts were elevated relative to controls on days 97 and 104 and were greater for T20 vs T7 and CTL gilts on day 110 (P < 0.05). There were no treatment effects (P > 0.1) on parenchymal or extraparenchymal tissue weights, or on epithelial proliferation as measured by immunohistochemistry for Ki-67. Treatments did not alter concentrations of dry matter (DM), fat, or DNA (P > 0.1) in parenchyma. Concentrations of RNA (P < 0.05) and protein (P < 0.10) as well as total parenchymal protein, RNA, and DNA (P < 0.05) were lower, or tended to be, in T20 than T7 or CTL gilts. Hyperprolactinemia for 20 d in late gestation increased mRNA abundance of the milk protein genes beta-casein (CSN2) and whey acidic protein (WAP) (P < 0.05) in mammary parenchyma and also decreased mRNA abundance of the long form of the prolactin receptor (PRLR-LF). Increasing PRL concentrations for 7 or 20 d in late gestation had no beneficial effects on the composition of the mammary gland, and sustained exposure to domperidone for 20 d reduced metabolic activity either by a lower expression of the long form of the PRL receptor in mammary parenchymal tissue or, most likely, by the early involution of parenchymal tissue. In conclusion, results do not support the hypothesis that a sustained hyperprolactinemia in late gestation could enhance mammary development of gilts.

该项目的目的是确定持续高泌乳素血症持续7或20天对晚期妊娠母猪的乳腺发育的影响。在妊娠的第90天，将小母猪分为3组之一，接受肌肉注射（IM）注射（1）菜籽油（CTL，n = 18），直到妊娠的第109±1天。（2）多巴胺受体拮抗剂多潘立酮（0.5 mg / kg体重[BW]）直至妊娠第96±1天（T7，n = 17）；或（3）多潘立酮（0.5 mg / kg体重），直到妊娠109±1天（T20，n = 17）。从妊娠90到93天，接受多潘立酮治疗的小母猪每天两次口服100 mg多潘立酮。在第89、97、104和110天抽取血液进行催乳素（PRL），胰岛素样生长因子1（IGF1），乳糖，尿素和葡萄糖检测。在第110天，尸检时收集乳腺，用于成分和细胞增殖分析。还在乳腺和垂体中确定了所选基因的mRNA丰度。在妊娠第97天，T20和T7母猪的PRL浓度是CTL母猪的3倍，T20的PRL浓度也高于T7和CTL母猪的104和110天（P <0.001）。T20和T7母猪的IGF1浓度在第97天和104天相对于对照升高，而T20和T7和CTL母猪的IGF1浓度在第110天更高（P <0.05）。通过Ki-67的免疫组织化学测定，对实质或实质外组织重量或上皮增殖没有治疗作用（P > 0.1）。治疗未改变实质中干物质（DM），脂肪或DNA的浓度（P > 0.1）。RNA（P <0.05）和蛋白质（P <0.10）以及总的实质蛋白，RNA和DNA（P<0.05）在T20中比T7或CTL后备母猪低或倾向于T20。妊娠后期高催乳素血症20 d增加了乳蛋白基因β-酪蛋白（CSN2）和乳清酸性蛋白（WAP）的mRNA丰度（P<0.05）在乳腺实质中，并且也降低了催乳素受体（PRLR-LF）的长形式的mRNA丰度。妊娠后期增加PRL浓度7或20 d对乳腺的组成没有有益的影响，并且持续暴露于多潘立酮20 d会降低代谢活性，这可能是由于PRL受体在乳腺实质中的低表达所致组织或最有可能通过实质组织的早期复旧。总之，结果不支持这样的假说，即妊娠后期持续的高泌乳素血症可以促进后备母猪的乳房发育。