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首页> 外文期刊>The Journal of Experimental Biology >MG2+ TRANSPORT IN PLASMA MEMBRANE VESICLES OF RENAL EPITHELIUM OF THE MOZAMBIQUE TILAPIA (OREOCHROMIS MOSSAMBICUS)
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MG2+ TRANSPORT IN PLASMA MEMBRANE VESICLES OF RENAL EPITHELIUM OF THE MOZAMBIQUE TILAPIA (OREOCHROMIS MOSSAMBICUS)

机译：MG2 +在莫桑比克T的肾上皮浆膜血管中的运输

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摘要

To elucidate the mechanisms involved in Mg2+ transport at the apical and basolateral poles of the renal tubular epithelium, apical and basolateral plasma membrane vesicle preparations were derived from kidney tissue of freshwater- and seawater-adapted Mozambique tilapia Oreochromis mossambicus. Brush-border preparations were enriched 15.8-fold in alkaline phosphatase activity and consisted almost exclusively of right-side-out membrane vesicles, Basolateral membrane preparations were enriched 7.5-fold in Na+/K+-ATPase activity and contained resealed vesicles and leaky membrane fragments, Mg2+ association with brush-border and basolateral plasma membranes, traced using radioactive Mg-27, occurred in an osmotically active space, In all instances, Mg2+ binding to the vesicular membrane was low compared with the vesicular uptake, Mg2+ equilibration across the vesicular membrane of brush-border preparations was rapid and sensitive to the presence of extravesicular Ca2+, suggesting that the apical membrane of the renal epithelium contains a transport pathway for divalent cations, Application of various ionic gradients did not affect vesicular Mg2+ transport in apical and basolateral membrane preparations, suggesting the presence of an ion-coupled transport mechanism, ATP or ATP-gamma-S did not stimulate Mg2+ fluxes, indicating that Mg2+ transport does not proceed via an ATP-driven or activated transporter, In these aspects, vesicular Mg2+ transport was similar in seawater and freshwater preparations, These results suggest that the apical membrane of renal epithelial cells lacks an active secretory Mg2+ transport mechanism, We propose that the Mg2+ conductivity of the apical membrane reflects a route for downhill Mg2+ entry and is involved in renal Mg2+ reabsorption. [References: 50]
机译：为了阐明Mg2 +在肾小管上皮的顶极和基底外侧极转运的机制，从淡水和海水适应性莫桑比克罗非鱼莫桑比克罗非鱼的肾脏组织中提取了顶极和基底外侧质膜囊泡制剂。刷式边界制剂的碱性磷酸酶活性富集15.8倍，几乎完全由右侧向外的膜囊泡组成;基底外侧膜制剂的Na + / K + -ATPase活性富集7.5倍，并且包含重新密封的囊泡和渗漏的膜碎片， Mg2 +与刷状边界和基底外侧质膜的结合（使用放射性Mg-27追踪）发生在渗透活性空间中。在所有情况下，与囊泡吸收相比，Mg2 +与囊泡膜的结合均较低，Mg2 +在整个囊泡膜上的平衡刷式边界制剂对囊泡外Ca2 +的存在是快速且敏感的，这表明肾上皮的顶膜包含二价阳离子的转运途径。各种离子梯度的应用并不影响在顶膜和基底外侧膜制剂中囊泡Mg2 +的转运，提示存在离子耦合的传输机制ATP或ATP-gamm aS不能刺激Mg2 +通量，表明Mg2 +的转运不是通过ATP驱动或活化的转运蛋白进行的。在这些方面，海水和淡水制剂中的囊泡Mg2 +转运是相似的，这些结果表明肾上皮细胞的顶膜缺乏一个活跃的分泌性Mg2 +转运机制，我们建议心尖膜的Mg2 +电导率反映下坡Mg2 +进入的途径，并参与肾脏Mg2 +的重吸收。 [参考：50]

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