Iron uptake by rabbit intestinal mucosal membrane vesicles.
Iron uptake by rabbit intestinal mucosal membrane vesicles.
复制标题
兔肠粘膜囊泡对铁的吸收。
DOI：
10.1016/0005-2736(81)90418-1
复制
发表时间：
1981
期刊：
影响因子：
--
通讯作者：
Aisen,P
中科院分区：
文献类型：
--
作者：
Marx,JJ;Aisen,P
用快速过滤技术研究了兔小肠刷状缘膜囊对铁的摄取。特别注意避免Fe(III)中铁的水解和Fe(II)中铁的氧化。研究了从含有柠檬酸铁的介质中吸收Fe(III)的情况，柠檬酸铁摩尔超量为铁的1000倍，计算结果足以防止简单的水解和多核络合物的形成。Fe(III)以一种温度依赖且可饱和的方式结合到粘膜上。然而，无法证明进入囊泡内间隙的运输。膜蛋白热变性后对Fe(III)的吸收几乎相同，这可能排除了特定蛋白受体的参与。在pH较低且柠檬酸与铁的摩尔比仅为20倍时，膜对Fe(III)的结合力较高。~(55)Fe(III)的大部分与膜结合很强，不能用过量的未标记Fe(III)清洗来去除。在相似的实验条件下，从抗坏血酸与铁的摩尔过量为20倍的介质中对Fe(II)的吸收比Fe(III)的吸收高数百倍。同样，正常囊泡和煮沸小泡对Fe(II)的摄取没有差异。然而，与Fe(III)的结果相反，可以证明Fe(II)被渗透空间吸收。大量的Fe(II)转运可以通过假设囊腔内的铁陷阱来解释，可能是由囊腔内的氧化和水解提供的。我们的发现表明，微绒毛膜囊泡对铁的吸收可能包括结合和简单扩散两种方式。
Iron uptake by brush border membrane vesicles isolated from rabbit small intestine was studied using a rapid filtration technique. Special attention was directed at avoiding hydrolysis of iron at Fe(III) and oxidation of iron at Fe(II). Uptake of Fe(III) was studied from media containing ferric citrate with a 1000-fold molar excess of citrate to iron, calculated to be sufficient to prevent simple hydrolysis and polynuclear complex formation. Fe(III) bound to the mucosal membranes in a temperature-dependent and saturable fashion. Transport into the intravesicular space, however, could not be demonstrated. Fe(III) uptake was almost identical after heat denaturation of membrane proteins, which probably rules out the involvement of a specific protein receptor. Membrane binding of Fe(III) was higher when media with a lower pH were used and when there was only a 20-fold molar excess of citrate to iron. The major part of the55Fe(III) is bound to the membranes very strongly, and cannot be removed by washing with excess unlabeled Fe(III). Under similar experimental conditions uptake of Fe(II), from a medium with a 20-fold molar excess of ascorbate to iron, was several hundred times higher than that of Fe(III). Again, there was no difference between the uptake of Fe(II) by normal or boiled vesicles. In contrast to results with Fe(III), however, uptake of Fe(II) into an osmotic space could be demonstrated. The large amount of Fe(II) transported may be explained by assuming an intravesicular iron trap, possibly provided by oxidation and hydrolysis in the vesicular lumen. Our findings indicate that the uptake of iron by microvillous membrane vesicles probably entails both binding and simple diffusion.