权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Molecular aspect of ascorbate transport system and its application for evaluation of toxicity of envioronmental pollutants

抗坏血酸转运系统的分子特征及其在环境污染物毒性评价中的应用

基本信息

批准号：
05671818
负责人：
MUTO Norio
金额：
$ 1.28万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05671818/
关键词：
Ascorbic acid Ascorbate-binding protein Membrane transport Toxicity evaluation

项目摘要

(1) In order to clarify the molecular aspect of ascorbate transport system, membraneous ascorbatebinding activity was studied by using CHAPS-solubilized preparation of rat kidney membranes. This binding activity was effectively inhibited by the addition of ascorbate and a high dose of dehydroascorbate, whereas glucose and glucose-transport inhibitors showed no inhibition.Moreover, this preparation was found to bind the reduced form of ascorbate, strongly supporting the presence of an ascorbate-specific binding protein which is considered to be a member of its transport system on the plasma membranes. (2) This binding protein was separated by gel filtration with a good retention of activity and its molecular weight was estimated to be about 100kDa. However, further purification was not achieved by any chromatography until now, resulting in remarkable decrease of activity. For its purification, it is necessary to establish the conditions to reconstitute the binding complex. (3) In this project we have found for the first time that gastric ascorbate secretion is mediated via cholinergic receptor and this mechanism is responsible for physiological importance of ascorbate in the stomach. In addition, the absorption efficiency of ascorbate in the small intestine was found to be influenced by nicotine. These results suggest that environmental pollutants dynamically affect the transport system of ascorbate in the gut. We need further investigation to establish ascorbate-specific uptake system of cell line for evaluation of toxicity by pollutants.

(1)为了阐明抗坏血酸转运系统的分子方面，用CHAPS溶解的大鼠肾膜制备物研究了膜抗坏血酸结合活性。这种结合活性可被抗坏血酸和高剂量脱氢抗坏血酸有效地抑制，而葡萄糖和葡萄糖转运抑制剂则没有抑制作用。此外，该制剂被发现与还原型抗坏血酸结合，强烈支持抗坏血酸特异结合蛋白的存在，该结合蛋白被认为是其质膜运输系统的成员。(2)该结合蛋白经凝胶过滤后活性保持较好，其相对分子质量约为100 kDa。然而，到目前为止，任何层析都没有实现进一步的纯化，导致活性显著下降。为了纯化它，有必要建立重新构建结合络合物的条件。(3)首次发现胃抗坏血酸的分泌是通过胆碱能受体介导的，这一机制是抗坏血酸在胃中发挥重要生理作用的机制之一。此外，尼古丁还影响了抗坏血酸在小肠中的吸收效率。这些结果表明，环境污染物动态影响抗坏血酸在肠道中的运输系统。我们还需要进一步的研究来建立细胞系抗坏血酸特异性摄取系统来评估污染物的毒性。