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Growth in pigs is regulated in large part by the brain neuroendocrine growth hormone (GH)-insulin-like growth factors (IGFs) axis [1]. The complex neuroendocrine control of GH release has been extensively reviewed [2,3]. In essence, the chief hypothalamic regulators of GH release are growth hormone releasing hormone (GHRH) and somatostatin (SS), which are subject to modulation by other hypothalamic peptides and by complex networks of neurotransmitter neurons. GHRH is able not only to stimulate pituitary GH secretion but also promote hypothalamic SS output，thus starting an autoregulatory circuit, whereas SS inhibits both GH release from the pituitary gland and GHRH secretion from the hypothalamus. The inhibiting action of SS may provide an alternative means of accelerating growth because the 14 or 28 amino acid residuals of SS containing an S-S bond are potent inhibitors of endogenous GH secretion [1]. One of the more elegant techniques is represented by the active or passive immunization of animals against endogenous regulatory peptides, for instance, SS, to immunoneutralize them [1,4,5]. In fact, the application of this method in endocrinology has proven to be feasible and has provided remarkable success in some tests with rats，sheep, and fish [5–8]. However, the growth-promoting effects of anti-SS require further studies, as the results obtained to date provide reasons for optimism with regard to the application of this methodology for the examination of pig growth physiology. CS is an agent that works as a specific inhibitor of SS in animal production to affect the endocrine system and improve the growth rate of fish, piglets, and finishing pigs [8–10]. Thus, CS may become a new candidate as a growth-promoter for pigs. Previous experiments involving rats, sheep, fish, and piglets have demonstrated that CS increases GH secretion [5–7,9,11,12]. The increase in GH secretion is possibly due to the decreasing levels of SS in the tissue and hypothalamus in response to the action of CS. The production of IGF-I depends on the actions of GH. IGF-I produced by the liver and other tissues is considered to be the prime effector of GH actions on growth and development. IGF-I produced by the liver is secreted into the circulation and has an endocrine action on target tissues [13,14]. In addition, IGF-I is also produced in most extrahepatic tissues and can function as an autocrine and/or paracrine growth stimulator [13,14]. The biological actions of IGF-I are mediated mainly through the IGF-I receptor (IGF-IR), and partly through the insulin receptor (IR) [15]. Furthermore, IGF binding proteins (IGFBPs) are important modulators of the biological actions of IGF [16]. However, there is no information about continuous long-term CS supplementation on the secretion and gene expression of the IGF system in any mammalian in vivo system. CS, as a novel growth promoter, is affected in animals by many factors: species of the animal, feeding time, feeding dosage, and chemical stability. Low doses of CS increase the average daily weight gain (ADG) and the average daily feed intake (ADFI) and higher doses of CS have no effect on ADG and ADFI in piglets and finishing pigs.12,13 Moreover, CS supplementation reduces back-fat thickness.13 in vitro study that CS is a reducing aminothiol, which has antioxidant capacity and increases embryo development.20 It can stimulate intracellular glutathione (GSH) production, 21,22 which could protect cells against thiol-derived peroxide. GSH acts as an oxidizable substrate of GSH-Px and as a direct scavenging agent.23 Little information, however, is known on the effects of chronic CS supplementation in meat quality, antioxidation, and carcass characteristics in finishing pigs. We have tested the hypothesis that chronic CS supplementation may affect carcass characteristics, meat quality, and antioxidant status in finishing pigs. In addition, in order to explore the mechanism responsible for the growth-promoting effect of CS supplementation, we have also tested the hypothesis that chronic CS supplementation may affect serum IGF-I concentrations and IGF-I, IGF-IR, IGFBP-3, and IR mRNA levels in different tissues of finishing pigs. |
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2楼2008-03-07 15:41:27
questwz
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生长在猪体内的调节在很大程度上是由脑内分泌生长激素（ GH ） ，胰岛素样生长因子（ igfs ）轴[ 1 ] 。复杂的神经内分泌控制的生长激素释放，也得到了广泛检讨[ 2,3 ] 。从本质上讲，行政监管下丘脑生长激素释放的生长激素释放激素（ ghrh ）和生长抑素（ SS ） ，这是一种受调制其他下丘脑多肽和复杂的网络，神经递质的神经元。 ghrh是不仅可以刺激垂体生长激素的分泌，但也能促进下丘脑的SS输出，从而开始了一个autoregulatory电路，而晚上都抑制生长激素释放垂体和ghrh分泌由下丘脑。 抑制行动的SS可能提供了一种新方法，加速经济增长，因为14或28个氨基酸残渣的SS含有的SS键是强效抑制剂内源性生长激素分泌[ 1 ] 。其中一个比较优雅的技术代表是主动还是被动免疫的动物对内源性调节肽，例如，悬浮物，以immunoneutralize他们[ 1,4,5 ] 。事实上，这种方法的应用，在内分泌学已证明是可行的，并提供了显著成绩，并在一些测试与鼠，羊，鱼[ 5-8 ] 。不过，持续增长促生作用的抗ss需要进一步研究，为迄今所取得的成果提供了乐观的理由方面的应用这一方法，为考试的猪生长生理学。 政务司司长是一个代理工程作为一项具体抑制剂的SS在畜牧生产中，影响内分泌系统和完善的增长率鱼，仔猪，育肥猪[ 8-10 ] 。因此，政务司司长有可能成为新的候选人，作为一个以增长促猪。以前的实验涉及鼠，羊，鱼，和仔猪已表明，政务司司长增加生长激素分泌[ 5-7,9,11,12 ] 。增加生长激素分泌可能是由于日渐减少的SS在组织和下丘脑响应行动的政务司司长。生产中IGF - I依赖于行动的生长激素。胰岛素样生长因子产生，由肝脏和其他组织中已被视为首要效应生长激素行动，对经济增长和发展。胰岛素样生长因子产生，由肝脏分泌进入流通，并具有内分泌行动，对目标组织[ 13,14 ] 。此外，胰岛素样生长因子I是，也产生了在大多数肝外组织和功能，可以作为一个自分泌和/或旁生长刺激因子[ 13,14 ] 。生物行动的胰岛素样生长因子-我导的，主要是通过胰岛素样生长因子受体（胰岛素样生长因子-红外） ，并部分通过胰岛素受体（ IR ）的[ 15 ] 。此外，胰岛素样生长因子结合蛋白（ igfbps ）是重要的调制器的生物行动的胰岛素样生长因子[ 16 ] 。不过，目前并无资料，连续长期政务司司长补充剂就分泌和基因表达的IGF系统在任何哺乳动物体内系统。 政务司司长，作为一种新型的生长促进剂，是影响动物受许多因素：物种的动物，喂养时间，喂养剂量，和化学稳定性。低剂量的政务司司长增加，平均每天体重增加（日增重） ，平均每日采食量（ adfi ）和高剂量的政务司司长是没有影响日增重和adfi在仔猪和整理pigs.12 ， 13此外，政务司司长补充剂降低后勤发thickness.13体外研究，政务司司长是一个减少aminothiol ，其中有抗氧化能力，并提高胚胎development.20它可以刺激细胞内谷胱甘肽（ GSH ）的生产， 21,22 ，可以保护细胞对硫醇源性过氧化物。总参作为一氧化基板的谷胱甘肽过氧化物酶和作为直接清除agent.23的资料很少，但是，众所周知，对影响慢性政务司司长补充，在肉类的质量，抗氧化，及胴体品质的育肥猪。我们已经测试了该假说认为，慢性政务司司长补充剂可能会影响胴体品质，肉质，抗氧化状态，在肥育猪。此外，为了探索机制，负责为促生长作用的政务司司长补充，我们也检验假设，即慢性政务司司长补充剂可能会影响血清IGF - I浓度和胰岛素样生长因子I型，胰岛素样生长因子-红外及IGFBP - 3 ，和IR mRNA水平在不同组织中的肥育猪。 |
3楼2008-03-07 19:41:31