Renal proximal tubule of flounder II. Transepithelial Mg secretion.
Renal proximal tubule of flounder II. Transepithelial Mg secretion.
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牙鲆的肾近端小管 II.
DOI：
10.1152/ajpregu.1986.250.4.r616
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Beyenbach,KW
中科院分区：
文献类型：
--
作者：
Cliff,WH;Sawyer,DB;Beyenbach,KW
在离体灌流的比目鱼（Pseudopleuronectes americanus）近端小管II中研究了镁的跨上皮分泌动力学。为了检测管腔[Mg]作为浴[Mg]的函数的可测量变化，必须以亚纳升速率灌注管腔。跨上皮镁分泌不遵守一级反应动力学，因此半饱和运输（0.22 mM）和运输最大值（1.5 pmol X min-1 X mm-1）的值是明显的，并建议高亲和力低容量运输系统。由于所有实验都是在没有浴SO 4的情况下进行的，因此建立了Mg运输与SO 4运输的独立性。在没有灌注的情况下，当小管自发分泌液体时，分泌的液体含有Cl（156 +/- 3 mM）、Na（130 +/- 6 mM）和Mg（27 +/- 5 mM），所有这些都与浴显著不同。Cl、Na和Mg的分泌速率均与体液分泌呈正相关，但分泌液中Na和Mg浓度呈反比。结果表明，NaCl的分泌提供了基础率的液体分泌，并且当MgCl 2被分泌另外，液体分泌增加的效果，产生腔Na和Mg浓度之间的反比关系。
The kinetics of transepithelial Mg secretion were studied in isolated perfused proximal tubule II of the flounder, Pseudopleuronectes americanus. To detect measurable changes of luminal [Mg] as a function of bath [Mg], the lumen had to be perfused at subnanoliter rates. Transepithelial Mg secretion did not obey first-order reaction kinetics; hence values for half saturation of transport (0.22 mM) and transport maximum (1.5 pmol X min-1 X mm-1) are apparent and suggest a high-affinity low-capacity transport system. Because all experiments were done in the absence of bath SO4, the independence of Mg transport from SO4 transport is established. In the absence of perfusion, when tubules secrete fluid spontaneously, secreted fluid contained Cl (156 +/- 3 mM), Na (130 +/- 6 mM), and Mg (27 +/- 5 mM), all significantly different from the bath. Rates of Cl, Na, and Mg secretion were all positively correlated with fluid secretion, but Na and Mg concentrations in secreted fluid were inversely proportional. The results indicate that NaCl secretion provides basal rates of fluid secretion, and when MgCl2 is secreted in addition, fluid secretion increases with the effect of generating inverse relationships between luminal Na and Mg concentrations.