Mitochondrial carbonic anhydrase is involved in rat renal glucose synthesis.
Mitochondrial carbonic anhydrase is involved in rat renal glucose synthesis.
复制标题
线粒体碳酸酐酶参与大鼠肾葡萄糖合成。
DOI：
10.1152/ajpendo.1989.257.6.e791
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Cherian,K
中科院分区：
文献类型：
--
作者：
Dodgson,SJ;Cherian,K
在37 ℃，pH 7.4时，破坏的大鼠肾近端小管和皮质线粒体的碳酸酐酶活性（kenz）分别为2.5 +/- 0.8（n = 3）和0.15 +/- 0.40（n = 3）ml.mg-1.s-1。肾线粒体碳酸酐酶（CA V）的转换数为24，000 s-1。0.15 μ M乙氧唑胺（EZ）可完全抑制完整线粒体的CA V活性。将从48小时饥饿雄性大鼠制备的完整近端小管在37 ℃下在含10 mM丙酮酸盐的Krebs-Henseleit碳酸氢盐缓冲液（5% CO2-95% O2）中孵育。通过在孵育溶液中包括0.6 μ M EZ，60分钟内的葡萄糖合成速率降低50%。将NaHCO 3的浓度加倍至50 mM（NaCl相应减少），并且用10%CO2 - 90%O2; 2.4 μ M EZ充气的溶液不再降低葡萄糖合成。由此得出结论，EZ抑制葡萄糖合成是抑制碳酸酐酶的直接结果。随后，在不含HCO 3（-）的N-2-羟乙基哌嗪-N '-2-乙磺酸（HEPES）缓冲液中孵育小管，测定葡萄糖产生速率; 0.6 μ M EZ使该速率降低50%。这些数据支持CA V为丙酮酸羧化酶提供HCO 3-和CO2可由肾小管代谢提供的假设。将完整的小管在5至20 mM丙酮酸中（25或50 mM HCO 3-）孵育;在任一缓冲液中，葡萄糖合成速率相似，随丙酮酸浓度增加而增加。在没有丙酮酸浓度的情况下，当小管在含有1.6 μ M EZ的50 mM HCO 3缓冲液中孵育时，葡萄糖产生速率发生变化。这些数据也支持的假设，CA V提供了丙酮酸羧化的HCO 3-底物时，有一个高速率的细胞内CO2的生产和外部CO2是低的。进一步得出结论，胞质碳酸酐酶（CA II）和膜结合碳酸酐酶（CA IV）不参与丙酮酸葡萄糖合成。
At 37 degrees C, pH 7.4, carbonic anhydrase activity (kenz) of disrupted rat renal proximal tubules and cortical mitochondria was 2.5 +/- 0.8 (n = 3) and 0.15 +/- 0.40 (n = 3) ml.mg-1.s-1, respectively. Turnover number for renal mitochondrial carbonic anhydrase (CA V) was 24,000 s-1. CA V activity of intact mitochondria was completely inhibited by 0.15 microM ethoxzolamide (EZ). Intact proximal tubules, prepared from 48-h starved male rats, were incubated at 37 degrees C in 10 mM pyruvate in Krebs-Henseleit bicarbonate saline buffer, 5% CO2-95% O2. The rate of glucose synthesis over 60 min was reduced 50% by including 0.6 microM EZ in the incubation solution. The concentration of NaHCO3 was doubled to 50 mM (with a corresponding decrease in NaCl) and the solution gassed with 10% CO2-90% O2; 2.4 microM EZ no longer decreased glucose synthesis. It was concluded that inhibition of glucose synthesis by EZ was directly a result of inhibiting the carbonic anhydrases. The rate of glucose production was subsequently determined with tubules incubating in a HCO3(-)-free N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid (HEPES) buffer; this rate was decreased 50% by 0.6 microM EZ. These data support the hypotheses that CA V provides HCO3- for pyruvate carboxylase and that CO2 can be provided by tubular metabolism. Intact tubules were incubated in from 5 to 20 mM pyruvate in either 25 or 50 mM HCO3-; in either buffer, the rate of glucose synthesis was similar, increasing with increasing pyruvate concentration. At no pyruvate concentration was there a change in the rate of glucose production when tubules were incubated in 50 mM HCO3- buffer with 1.6 microM EZ. These data also support the hypothesis that CA V provides the HCO3- substrate for pyruvate carboxylation when there is a high rate of intracellular CO2 production and external CO2 is low. It is further concluded that the cytosolic carbonic anhydrase (CA II) and the membrane-bound carbonic anhydrase (CA IV) are not involved in glucose synthesis from pyruvate.