No effect of vitamin D3 treatment on active calcium absorption across ruminal epithelium of sheep.-猫眼课题宝

维生素 D3 处理对绵羊瘤胃上皮的活性钙吸收没有影响。

DOI：

发表时间：

2001

期刊：

Journal of veterinary medicine. A, Physiology, pathology, clinical medicine

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

B. Schröder;W. Goebel;K. Huber;G. Breves

在不同反刍动物种属的体内和体外研究中，已经假定前胃对胃肠道净钙（Ca 2+）吸收的重要贡献。然而，维生素D3及其代谢产物在控制这些机制中的潜在作用仍在讨论中。因此，本研究的目的是研究维生素D3处理在刺激绵羊瘤胃活性钙吸收的有效性。四个成熟的，非哺乳期，非怀孕的羊，已处理7和4天前的Ca 2+通量率测量与肌肉注射300000 IU的维生素D3的水溶液。2只雌性和3只雄性安慰剂给药绵羊作为对照。为了表征维生素D3应用对血浆参数的影响，记录了总钙、无机磷酸盐、骨化三醇和全段甲状旁腺激素（iPTH）的时程。应用Ussing小室技术，在体外研究了游离完整瘤胃壁上皮细胞的单向钙流率。采用Western blot和RT-PCR技术对瘤胃和空肠组织中的维生素D受体（VDR）进行了鉴定。此外，在这些组织中进行用于定性检查上皮钙结合蛋白D9 k水平的蛋白质印迹分析。血浆中的总钙和磷酸盐水平没有显着影响治疗与维生素，而骨化三醇浓度显着增加约130和63%后，第一次和第二次应用程序，分别。相反，iPTH倾向于降低约60%，表明骨化三醇对全身Ca稳态的调节作用。在Ussing室中的Ca 2+通量率测量显示显着的净Ca 2+吸收，表明在瘤胃上皮细胞中的Ca 2+运输的积极机制的贡献。然而，血浆中骨化三醇浓度增加并不显著影响这一点。蛋白质印迹分析的基础上的人重组VDR蛋白和RT-PCR清楚地表明，VDR的存在下，在瘤胃和空肠上皮细胞，但是，与空肠相反，这并没有反映出相应的量的钙结合蛋白-D9 k在瘤胃组织。结果表明，缺乏经典的钙结合蛋白-D9 k介导的主动钙转运在绵羊瘤胃的机制。

A significant contribution of the forestomachs in net calcium (Ca2+) absorption from the gastrointestinal tract has been postulated from in vivo and in vitro studies in different ruminant species. However, the potential role of vitamin D3 and its metabolites in controlling these mechanisms is still under discussion. It was therefore the aim of the present study to investigate the effectiveness of treatment with vitamin D3 in stimulating active Ca2+ absorption from sheep rumen. Four mature, non-lactating, non-pregnant sheep that had been treated 7 and 4 days before the Ca2+ flux rate measurements with intramuscular injections of 300000 IU of vitamin D3 each in aqueous solution were used. Two female and three male placebo-treated sheep served as controls. To characterize the effects of vitamin D3 application on plasma parameters the time courses of total calcium, inorganic phosphate, calcitriol and intact parathyroid hormone (iPTH) were recorded. In vitro studies of unidirectional Ca2+ flux rates across isolated, intact rumen wall epithelia were carried out by applying the Ussing-chamber technique. Western blot analysis and reverse transcriptase-polymerase chain reaction analysis (RT-PCR) were applied to identify vitamin D receptors (VDR) in ruminal and jejunal tissues. In addition, Western blot analysis for qualitative examination of epithelial calbindin D9k levels was carried out in these tissues. Total calcium and phosphate levels in plasma were not significantly affected treatment with vitamin whereas calcitriol concentrations significantly increased by about 130 and 63% after the first and second application, respectively. In contrast, iPTH tended to decrease by about 60% indicating regulatory effects of calcitriol on systemic Ca homeostasis. The Ca2+ flux rate measurements in Ussing-chambers revealed significant net Ca2+ absorption indicating the contribution of active mechanisms for Ca2+ transport in rumen epithelia. This, however, was not significantly affected by increased calcitriol concentrations in plasma. Western blot analysis on the basis of a human recombinant VDR protein and RT-PCR clearly indicated the presence of VDR in ruminal and jejunal epithelia, but, in contrast to jejunum, this was not reflected by respective amounts of calbindin-D9k in ruminal tissues. The results suggest the absence of classical calbindin-D9k-mediated mechanisms for active Ca2+ transport in sheep rumen.

Purification of chicken intestinal receptor for 1 alpha, 25-dihydroxyvitamin D3 to apparent homogeneity.