泌乳期哺乳动物钙代谢研究进展

哺乳动物钙代谢包括钙平衡与钙稳态。钙平衡是指体内总钙含量保持相对恒定的状态,钙稳态则指细胞内外的钙离子浓度保持稳定。在哺乳动物的泌乳期,大量的钙流失到乳中,导致母体血清钙急剧下降。动物的肠道、肾脏、骨骼作为主要的钙代谢器官,将对此做出适应性改变,以维持哺乳动物在泌乳期的钙代谢稳态。哺乳动物钙代谢紊乱会严重影响母畜及幼崽的营养健康,给畜牧养殖业带来损失,因此,维持钙代谢稳态对泌乳期哺乳动物尤为重要。本文综合近年来国内外哺乳动物钙代谢相关研究,从哺乳动物泌乳期不同器官钙代谢适应性改变、血清钙和血清磷等矿物质以及钙调节因子的变化进行综述,旨在为泌乳期哺乳动物钙代谢调控的相关研究提供思路。     

鸡钙营养代谢及基因调控研究进展

钙是动物体内的必需营养元素之一，鸡体内的钙代谢直接关系到鸡生长和生产的发挥。随着生产性能的大幅提高，因钙代谢引发的相关疾病或问题日益突出，文章从鸡体内钙自主代谢调节及基因调控等方面，对鸡钙营养代谢的基因调控进行分析探讨。     

MAM在哺乳动物细胞中的研究进展

线粒体相关内质网膜（MAM）在调节稳态内质网转运到线粒体的钙信号传导、脂质代谢、自噬体的形成、线粒体的形态动力学功能、相关蛋白的调控功能以及细胞凋亡调节过程中都发挥着关键的作用,并对癌症和神经退行性等疾病起着调节作用。因此,对MAM生化特性和功能的了解至关重要。本文综述了近年来MAM在哺乳动物细胞中的研究进展,以期为今后 MAM 的相关研究提供参考。 [关键词] MAM|哺乳动物|线粒体|钙信号|调控功能     

动物钙营养代谢的基因调控探讨

钙是动物体内必需营养元素之一,钙代谢直接关系到畜禽生长和生产潜力的发挥。随着生产性能的大幅提高,因钙代谢引发的相关疾病或问题日益突出,本文从钙的吸收排泄、机体内自主代谢调节及基因调控等方面,对动物钙营养代谢的基因调控进行了分析探讨。     

TRPV5与TRPV6在哺乳动物妊娠期钙代谢的适应性调节作用

在哺乳动物妊娠期,母体的钙代谢通过适应性调节满足胎儿对钙的需求,包括肠钙吸收的增强、肾钙排泄的减少。妊娠钙代谢适应性需要钙离子通路蛋白参与,TRPV5/TRPV6是实现钙代谢调节的重要蛋白。TRPV6高表达于小肠,主要介导肠钙转运,TRPV5与肾脏钙离子重吸收相关,此外TRPV6介导胎盘组织的母体一胎儿钙转运。     

奶牛斯钙素-1研究进展

斯钙素(stanniocalcin, STC-1)最早是在硬骨鱼体内发现的一种糖蛋白激素,在鱼类具有抑制腮和肠对钙的摄入,促进肾脏对磷酸盐的吸收,防止血钙过高,对体内钙和磷酸盐的稳定起着重要的调节作用.近年来在人和其他哺乳动物体内发现也存在STC-1,哺乳动物斯钙素除了可调控体内矿物质代谢外,还具有更为广泛的功能,如对生殖和生长等生理过程的调控作用.STC-1在奶牛方面的研究尚处     

以锰为代表的过渡金属离子体内吸收及转运机制

<正>近年来,金属离子在生命体内的代谢、稳态平衡及其相关疾病是当前国际热点研究领域之一~([1])。微量元素是指生物体内含量不足万分之一的元素。在动物体内,微量元素虽然含量微小,但具有极其重要的生理功能,涉及生长发育、新陈代谢、内稳态调节、神经活动、免疫功能、氧化应激、信号转导、基因调控、酶及内分泌等几乎所有的生命活动过程~([2])。一方面,金属离子的存在对金属蛋白/金属酶结构的稳     

钙依赖蛋白激酶(CDPKs)介导植物信号转导的分子基础

钙依赖蛋白激酶(CDPKs)是生长发育信号和逆境信号诱发的钙信号的重要信号传递体,在调控植物信号转导途径中下游基因的表达、生化代谢、离子和水分跨膜运输等生物学过程中具有重要作用。本研究对植物种属CDPK的结构特点、CDPK在植株体内的分布特征、CDPK生理生化特性及生化反应调控特性、CDPK 在信号转导中的作用,以及CDPK在植株体内的生物学功能进行了概述。旨在为今后牧草作物CDPK的鉴定及其介导的信号转导机制的研究提供参考依据。     

钙磷代谢对动物骨骼健康影响的研究进展

骨骼构成机体结构的基本框架,骨形成和骨吸收的动态平衡关系到骨骼健康。钙和磷是动物体骨骼生长发育过程中重要的矿物质元素,机体对其吸收与调控直接影响骨代谢过程。血钙和血磷水平的变化,改变了机体相关调节激素的分泌,而这些激素可影响骨骼发育,因此,钙、磷代谢与骨骼健康紧密相关。综合国内外钙、磷代谢和骨代谢等方面的研究,从钙、磷的吸收和代谢,含量和比例以及钙磷代谢相关调节激素对骨骼发育的调控机制等方面进行综述,旨在为后续动物钙、磷代谢和骨骼之间调控的研究提供参考。     

钙信号转导调控动物胃肠道细胞增殖和功能的研究进展

胃肠道是动物营养吸收代谢的主要场所，调控胃肠道发育具有重要的生产意义和经济价值。钙离子是细胞内重要的第二信使，通过钙信号参与调控机体几乎所有生命活动，小到细胞收缩、胞吐，大到基因和蛋白表达、细胞增殖和凋亡以及组织、器官的发育。大量研究表明，调节钙信号可以预防和治疗心肺血管疾病，但是否可以通过调控钙信号促进胃肠道细胞增殖和功能完善的研究甚少。为此，本文在综述细胞钙内流和钙库释放的稳衡机制的基础上，分析了钙信号调节胃肠道细胞增殖和功能完善的可能途径，以期为通过营养途径调节钙信号促进动物胃肠道发育提供理论依据和路径。     

Calcium metabolism in birds.

Calcium is one of the most important plasma constituents in mammals and birds. It provides structural strength and support (bones and eggshell) and plays vital roles in many of the biochemical reactions in the body. The control of calcium metabolism in birds is highly efficient and closely regulated in a number of tissues, primarily parathyroid gland, intestine, kidney, and bone. The hormones with the greatest involvement in calcium regulation in birds are parathyroid hormone, 1,25-dihydroxyvitamin D(3) (calcitriol), and estrogen, with calcitonin playing a minor and uncertain role. The special characteristics of calcium metabolism in birds, mainly associated with egg production, are discussed, along with common clinical disorders secondary to derangements in calcium homeostasis.     

Hormonal regulation and calcium metabolism in the rabbit.

Calcium is an important mineral in homeostasis in all vertebrate animals. It is the most abundant mineral in the body, and is the major component of bones and teeth. In addition, calcium is involved in various vital physiologic processes, including blood coagulation, muscle contraction, membrane permeability, nerve conduction, enzyme activity, and hormone release. Calcium metabolism in the rabbit differs in several respects from that of most mammals. This article discusses calcium metabolism and its hormonal regulation in the rabbit, as compared with normal calcium metabolism in other mammalian species. Medical disorders associated with this unique metabolism are introduced briefly.     

动物细胞内锌稳衡调节的研究进展

锌是生命必需的微量元素,参与了细胞内许多不同的代谢过程。对生物体而言,细胞内锌的稳态平衡非常重要。维持细胞内锌稳态平衡的蛋白主要包括金属硫蛋白(MT)及Zn转运蛋白(ZnTs)。本文主要介绍了MT及ZnT对锌稳态平衡的调节及锌对二者基因表达的调节作用。     

Feeding 5-hydroxy-l-tryptophan during the transition from pregnancy to lactation increases calcium mobilization from bone in rats

An increasing demand for calcium during pregnancy and lactation can result in both clinical and subclinical hypocalcemia during the early lactation period in several mammalian species, in particular the dairy cow. Serotonin (5-HT) was recently identified as a regulator of lactation and bone turnover. The purpose of this study was to determine whether supplementation of the maternal diet with a 5-HT precursor would increase maternal bone turnover and calcium mobilization to maintain appropriate circulating maternal concentrations of ionized calcium during lactation. Female Sprague-Dawley rats (n = 30) were fed either a control diet (n = 15) or a diet supplemented with the 5-HT precursor 5-hydroxytryptophan (5-HTP, 0.2%; n = 15) from day 13 of pregnancy through day 9 of lactation. Maternal serum and plasma (day 1 and day 9 of lactation), milk and pup weight (daily), mammary gland and bone tissue (day 9 of lactation) were collected for analysis. The 5-HTP diet elevated circulating maternal concentrations of 5-HT on day 1 and day 9 of lactation and parathyroid hormone related-protein (PTHrP) on day 9 of lactation (P < 0.033). In addition, 5-HTP supplementation increased total serum calcium concentrations on day 1 of lactation and total milk calcium concentration on day 9 of lactation (P < 0.032). Supplemental 5-HTP did not alter milk yield, maternal body weight, mammary gland structure, or pup litter weights (P > 0.05). Supplemental 5-HTP also resulted in increased concentrations of mammary 5-HT and PTHrP, as well as increased mRNA expression of rate-limiting enzyme in 5-HT synthesis, tryptophan hydroxylase 1, and Pthrp mRNA on day 9 of lactation (P < 0.028). In addition, supplementation of 5-HTP resulted in increased mRNA expression of maternal mammary calcium transporters and resorption of bone in the femur, indicated by increase osteoclast number and diameter as well as mRNA expression of classical markers of bone resorption on day 9 of lactation (P < 0.048). These results show that increasing 5-HT biosynthesis during the transition from pregnancy to lactation could be a potential therapeutic target to explore for prevention of subclinical and clinical hypocalcemia.     

Effects of dietary cation-anion difference on blood cortisol and ACTH levels in reproducing ewes

Formulation of rations to induce a compensated metabolic acidosis in the post-partum cow has proved a useful strategy for prevention of milk fever. Such acidification improves the ability of the animal to maintain calcium homeostasis by promoting the absorption of calcium from the intestine and mobilization of calcium from the bone. In humans, an acidogenic diet results in mild metabolic acidosis in association with a state of cortisol excess and this increase in plasma cortisol may increase bone catabolism. The objective of our experiment was to induce acidification by anionic salt supplementation and to study the effects of anionic supplementation on plasma cortisol and adrenocorticotropic hormone (ACTH) levels in sheep. Twenty-seven twin-bearing sheep were assigned to two experimental groups and a control group, depending on dietary cation-anion difference (DCAD) (+272.6, -88.9 and +164.5 mEq/kg DM respectively). Sheep assigned to each dietary treatment received their respective rations beginning 6 weeks pre-partum and continuing until 12 days post-partum. Anionic diet induced a non-respiratory systemic acidosis in association with a mild increase in plasma cortisol concentration without changes in plasma ACTH levels. Our data suggest that the mild hypercortisolism observed in sheep fed the anionic diet may not be an effector for bone resorption induced by anionic salts. A mild hypercortisolism of this magnitude may lead to osteoporosis but this might require many years of adrenal hypersecretion while anionic salts are only used during the last weeks of pregnancy.     

Disorders of the parathyroid glands

The three calcitropic hormones, parathyroid hormone (PTH), 1,25-dihydroxycholecalciferol and calcitonin are together responsible for calcium homeostasis in the mammal. Feline PTH is an 84 amino acid, single chain polypeptide with a molecular weight of 9449, which is secreted by the parathyroid glands. The principle secretagogue for PTH is a low plasma ionised calcium concentration, although both 1,25-dihydroxycholecalciferol and phosphate have significant roles in regulating PTH secretion. The ability to accurately measure circulating PTH in the cat has simplified the evaluation of disorders of calcium metabolism in this species. In primary parathyroid disorders the lesion is located within the parathyroid gland, with parathyroid secretion being inappropriate to the prevailing mineral balance. By contrast, in secondary conditions a pathological state out with the parathyroid gland alters mineral homeostasis and the parathyroid gland responds in an appropriate manner. The measurement of circulating PTH may then be used to determine if PTH secretion is appropriate to the prevailing calcium concentrations to differentiate primary from secondary disorders. Although primary hyper and hypoparathyroidism are generally considered rare endocrine conditions of the cat, the ability to measure PTH has led to their increasing recognition.     

Metabolism of some essential minerals in ponies fed high levels of aluminum

The effect of dietary aluminum on the absorption, retention and pathways of excretion of calcium, phosphorus, magnesium, zinc, iron and copper was studied in balance trials in mature ponies in a three by three latin square experiment. A basal diet consisting of one third each of oats, beet pulp and a commercial pelleted, complete horse ration and containing 336 ppm aluminum was supplemented with AlC1(3) . 6H2O. The middle and high level aluminum diets contained 1370 and 4500 ppm aluminum respectively. There was little difference in effect between the middle level aluminum and basal diets. The ponies were in negative phosphorus balance when fed the high level aluminum diet because phosphorus absorption was suppressed. Calcium absorption was unaffected by aluminum intake but the ponies were in negative calcium balance when fed the high aluminum diet due to the greater urinary excretion of calcium by the ponies. Presumably, calcium was excreted in urine because it was not utilized in the formation of bone crystal due to the lack of phosphate. Plasma calcium was elevated and plasma phosphorus was depressed when ponies were fed the high aluminum diet. Plasma hydroxyproline concentration was increased suggesting that bone turnover was increased due to aluminum effects on phosphorus and calcium metabolism. Magnesium, zinc, iron and copper metabolism were unaffected by aluminum intake.