COMPARATIVE ASPECTS OF PLACENTAL LACTOGENS - STRUCTURE AND FUNCTION
COMPARATIVE ASPECTS OF PLACENTAL LACTOGENS - STRUCTURE AND FUNCTION
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DOI：
10.1055/s-0029-1211288
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发表时间：
1994-01-01
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影响因子：
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通讯作者：
FORSYTH, IA
中科院分区：
文献类型：
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作者：
FORSYTH, IA
从妊娠大鼠中取出垂体提供了胎盘是催乳素样生物活性来源的早期证据。妊娠中期后，胎盘能够通过黄体（促黄体活性）和乳腺的继续发育（促乳腺活性）支持孕酮的产生。目前已知啮齿类、反刍类、偶蹄类和灵长类三大类哺乳动物的胎儿胎盘都能产生与垂体催乳素和生长激素结构相关的多种蛋白质，催乳素和生长激素本身在结构上也有相关性，并被认为是通过基因复制和进化趋异从共同的祖先基因中产生的。与它们相互作用的受体也形成同源蛋白质家族。令人惊讶的是，胎盘催乳素似乎在进化中出现了不止一次，因为在灵长类动物中，它们在结构上与生长激素密切相关，而在啮齿动物和反刍动物中，它们与催乳素更相似。在人类17号染色体上有一个5基因簇，包含2个生长激素（GH）和3个胎盘催乳素（PL）基因。两个人PL基因编码在胎盘中表达的相同蛋白质。人类GH基因之一也在胎盘中表达。在小鼠中，13号染色体携带小鼠催乳素、胎盘催乳素-I和-II（PL-I和PL-II）以及另外两种催乳素相关蛋白-增殖素的基因。大鼠还表达PL-Ⅰ和PL-Ⅱ，以及至少三种不同于增殖素的其他胎盘催乳素样蛋白。在绵羊、山羊和奶牛中，胎盘催乳素与它们的同源催乳素具有约50%的序列同源性。牛胎盘也产生了cDNA克隆预测催乳素相关的蛋白质，但不同的FL。这些已知或预测的蛋白质的生理作用知之甚少。然而，每一个，似乎显示出一个相当具体的表达模式方面的组织，细胞和出现的时间。胎盘催乳素在母体血浆中可能达到非常高的浓度，其作用被认为包括在啮齿动物中的促黄体作用和在所有种属中将营养物质转移到胎儿的代谢作用以及对乳房发育的影响。它们也可能在胎儿发挥促进生长和代谢作用方面发挥重要作用。
Removal of the pituitary from pregnant rats provided early evidence that the placenta was the source of prolactin-like bioactivity. After mid-pregnancy the placenta was able to support progesterone production by the corpus luteum (luteotrophic activity) and continued development of the mammary gland (mammotrophic activity). Three groups of mammals, the rodents, the ruminant artiodactyls and the primates are now known to produce from fetal placenta a remarkable variety of proteins which are related in structure to pituitary prolactin and growth hormone.Prolactin and growth hormone are themselves structurally related and are thought to have arisen from a common ancestral gene by gene duplication and evolutionary divergence. The receptors with which they interact also form a family of homologous proteins. Surprisingly the placental lactogens appear to have arisen more than once in evolution since in primates they are structurally closely related to growth hormone, while in rodents and ruminants they have closer similarity to prolactin. There is suggestive evidence that there may be specific receptors for placental lactogens in some fetal and maternal tissues.In humans a five-gene cluster on chromosome 17 contains two growth hormone (GH) and three placental lactogen (PL) genes. Two human PL genes encode identical proteins that are expressed in the placenta. One of the human GH genes is also placentally expressed. In mice, chromosome 13 carries the genes for mouse prolactin, for placental lactogen-I and -II (PL-I and PL-II) and for two other prolactin-related proteins, the proliferins. Rats also express PL-I and PL-II, together with at least three other placental prolactin-like proteins different from proliferins. In sheep, goat and cow, placental lactogens with about 50% sequence homology with their homologous prolactins occur. The bovine placenta has also yielded cDNA clones predicting proteins related to prolactin but distinct from FL.The physiological role of most of these known or predicted proteins is poorly understood. Each, however, appears to show a rather specific pattern of expression with regard to tissue, cell and time of appearance. Placental lactogens may reach very high concentrations in maternal plasma and their roles are thought to include luteotrophic effects in rodents and in all species metabolic effects to divert nutrients to the fetus as well as effects on mammary development. They may also have important roles in the fetus exerting growth-promoting and metabolic actions.