Christian H C, Chapman L P, Morris J F
Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
J Neuroendocrinol. 2007 Aug;19(8):605-13. doi: 10.1111/j.1365-2826.2007.01567.x.
In the male rat anterior pituitary, three morphological subtypes of cells secreting primarily prolactin (PRL) (lactotrophs) have been described. Type I contain predominantly large irregularly shaped granules, whereas type II and type III lactotrophs contain smaller spherical granules. We have previously shown that oestradiol and testosterone exert a rapid stimulatory effect selectively on type II lactotrophs but it is not known how the lactotroph subtypes respond to peptide secretagogues. We have therefore examined which cell subtype(s) release PRL in response to vasoactive intestinal peptide (VIP), thyrotrophin-releasing hormone (TRH) and prolactin-releasing peptide (PrRP-31). Pituitary segments were incubated in medium containing tannic acid (to capture exocytosis of secretory granules), either alone or with secretagogue peptide. VIP (1-10 nM), TRH (10 nM) and PrRP-31 (10 nM) all caused a significant increase (P < 0.05) in the amount of PRL granule exocytosis from type II and III lactotrophs, but had no effect on PRL exocytosis from type I. Dopamine (100 nM) inhibited basal exocytosis of immunoreactive (ir)-PRL from type I, II and III lactotrophs and PrRP-31-stimulated ir-PRL granule exocytosis from II and III lactotrophs. Treatment of lactating female rats with the dopamine D(2) receptor antagonist sulpiride (40 microg/kg) produced a significant increase (P < 0.05) in PRL granule exocytosis from type I and type III lactotrophs and a significant increase (P < 0.05) in the proportion of type I and II cells undergoing exocytosis of PRL. In conclusion, VIP, TRH and PrRP-31 selectively stimulate exocytosis from type II and III lactotrophs in the male rat, whereas all three lactotroph types are sensitive to dopamine inhibition of exocytosis in male and female rats.
在雄性大鼠的垂体前叶中，已描述了三种主要分泌催乳素（PRL）的细胞形态亚型（催乳素细胞）。I型细胞主要含有大的不规则形状的颗粒，而II型和III型催乳素细胞含有较小的球形颗粒。我们之前已经表明，雌二醇和睾酮对II型催乳素细胞有选择性的快速刺激作用，但尚不清楚催乳素细胞亚型对肽类促分泌素的反应如何。因此，我们研究了哪些细胞亚型会对血管活性肠肽（VIP）、促甲状腺激素释放激素（TRH）和催乳素释放肽（PrRP-31）产生反应并释放PRL。将垂体片段单独或与促分泌素肽一起在含有单宁酸（用于捕获分泌颗粒的胞吐作用）的培养基中孵育。VIP（1-10 nM）、TRH（10 nM）和PrRP-31（10 nM）均导致II型和III型催乳素细胞中PRL颗粒胞吐量显著增加（P<0.05），但对I型细胞的PRL胞吐没有影响。多巴胺（100 nM）抑制I型、II型和III型催乳素细胞中免疫反应性（ir）-PRL的基础胞吐作用，并抑制PrRP-31刺激的II型和III型催乳素细胞中ir-PRL颗粒的胞吐作用。用多巴胺D(2)受体拮抗剂舒必利（40μg/kg）处理哺乳期雌性大鼠，导致I型和III型催乳素细胞中PRL颗粒胞吐显著增加（P<0.05），并且I型和II型细胞发生PRL胞吐的比例显著增加（P<0.05）。总之，VIP、TRH和PrRP-31选择性刺激雄性大鼠II型和III型催乳素细胞的胞吐作用，而所有三种催乳素细胞类型对雄性和雌性大鼠中多巴胺抑制胞吐作用均敏感。
