Substrate responses to acid-base alterations in dog renal proximal tubules.
Substrate responses to acid-base alterations in dog renal proximal tubules.
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狗肾近曲小管酸碱变化的底物反应。
DOI：
10.1152/ajprenal.1992.262.6.f1039
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Zweifel,K
中科院分区：
文献类型：
--
作者：
Simpson,DP;McSherry,N;Scarbrough,E;Zweifel,K
狗肾近端小管与低浓度的丙酮酸、谷氨酰胺和苹果酸孵育2-6分钟。当初始柠檬酸浓度为0~0.5 mM，α-酮戊二酸浓度为0~0.1 mM时，加入10 mM的HCO3-时，这两种底物在小管和培养基中的浓度均低于40 mM的HCO3-。肾小管和基质中的苹果酸水平呈相反方向变化。标记的柠檬酸盐或α-酮戊二酸在低浓度时比在高浓度的HCO3-时产生更多的二氧化碳。在用洋地黄素破坏细胞膜的小管中，在高HCO3-和低HCO3-时，小管中柠檬酸和α-酮戊二酸浓度的差异被消除。在洋地黄素预处理后，完整小管中的酸碱变化对苹果酸水平和标记的柠檬酸的氧化速率的影响仍然存在。这些结果表明，在完整的肾皮质中观察到的酸碱变化对柠檬酸、α-酮戊二酸和苹果酸水平的急性影响可以在分离的小管上复制。他们认为，这些变化与细胞质中柠檬酸和α-酮戊二酸水平的变化有关，而与线粒体内没有相应的变化有关。
Proximal tubules from dog kidney were incubated for 2-6 min with low concentrations of pyruvate, glutamine, and malate. When initial medium citrate was between 0 and 0.5 mM and alpha-ketoglutarate was between 0 and 0.1 mM, concentrations of these two substrates in tubules and media after incubation were lower with 10 than with 40 mM HCO3-. Malate levels in tubules and media changed in the opposite direction. CO2 formation from labeled citrate or alpha-ketoglutarate was greater at low than at high HCO3-. In tubules treated with digitonin to disrupt the cell membrane, differences in citrate and alpha-ketoglutarate concentrations in tubules at high and low HCO3- were eliminated. The effects of acid-base changes seen in intact tubules on malate levels and on the rate of oxidation of labeled citrate persisted after digitonin pretreatment. These results show that acute effects of acid-base changes on citrate, alpha-ketoglutarate, and malate levels observed in intact renal cortex can be reproduced in isolated tubules. They suggest that these changes are related to changes in levels of citrate and alpha-ketoglutarate in cytoplasm without corresponding changes within mitochondria.