完整肝脏内质网中细胞色素P-450依赖的药物氧化过程中的肝脏钙外流。

Hepatic calcium efflux during cytochrome P-450-dependent drug oxidations at the endoplasmic reticulum in intact liver.

作者信息

Sies H, Graf P, Estrela J M

出版信息

Proc Natl Acad Sci U S A. 1981 Jun;78(6):3358-62. doi: 10.1073/pnas.78.6.3358.

DOI:10.1073/pnas.78.6.3358

PMID:6943544

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC319567/

Abstract

During metabolism of (type I) drugs by cytochrome P-450-dependent monooxygenase of the endoplasmic reticulum, the NADPH/NADP+ ratio in rat liver selectively decreases to approximately one-half of the control values, whereas the NADH/NAD+ ratio remains practically unaffected [Sies, H. & Brauser, B. (1970) Eur. J. Biochem. 15, 521-540]. In view of the observations with isolated mitochondria [Lehninger, A. L., Vercesi, A. & Bababunmi, E. A. (1978) Proc. Natl. Acad. Sci. USA 75, 1690-1694] of stimulated Ca2+ efflux upon nicotinamide nucleotide oxidation, the selective oxidation of NADPH in cytosol and mitochondria during drug oxidations was considered a useful experimental tool for the determination of whether the oxidation of NADPH or of NADH is responsible for Ca2+ efflux. With perfused livers from phenobarbital-treated rats, Ca2+ efflux was demonstrated, amounting to 8 nmol/min per gram of liver (wet weight), with aminopyrine, ethylmorphine, or hexobarbital as drug substrates. Drug-associated Ca2+ release was diminished when the inhibitor metyrapone was also present, or when drug oxidation was suppressed during N2 anoxia or in the presence of antimycin A in livers from fasted rats. Ca2+ efflux was elicited also by infusion of the thiol oxidant diamide, and by t-butyl hydroperoxide. However whereas Ca2+ efflux elicited by these compounds was restricted upon addition of the thiol dithioerythritol, there was little, if any, sensitivity of the drug-associated Ca2+ efflux to the thiol. Further mitochondrial oxidation of NADPH by addition of ammonium chloride had no effect on drug-associated Ca2+ efflux. Prior addition of the alpha-agonist phenylephrine suppressed the Ca2+ release by drug addition. While the molecular mechanism involved in Ca2+ efflux from liver mitochondria and from hepatocytes as well as the regulatory significance are not yet known, it is concluded from the present experiments that in case of nicotinamide nucleotide-linked Ca2+ efflux the oxidation of NADPH may suffice, with oxidation of NADH not being a requirement.

摘要

在内质网中细胞色素P - 450依赖性单加氧酶对（I型）药物进行代谢的过程中，大鼠肝脏中的NADPH/NADP⁺比值选择性地降至对照值的约二分之一，而NADH/NAD⁺比值实际上未受影响[Sies, H. & Brauser, B. (1970) Eur. J. Biochem. 15, 521 - 540]。鉴于对分离线粒体的观察结果[Lehninger, A. L., Vercesi, A. & Bababunmi, E. A. (1978) Proc. Natl. Acad. Sci. USA 75, 1690 - 1694]，即烟酰胺核苷酸氧化时会刺激Ca²⁺外流，在药物氧化过程中细胞质和线粒体中NADPH的选择性氧化被认为是一种有用的实验工具，用于确定是NADPH的氧化还是NADH的氧化导致了Ca²⁺外流。对于用苯巴比妥处理过的大鼠的灌注肝脏，以氨基比林、乙基吗啡或己巴比妥作为药物底物时，可证明有Ca²⁺外流，其量为每克肝脏（湿重）8 nmol/分钟。当存在抑制剂美替拉酮时，或者在禁食大鼠肝脏中N₂缺氧期间或存在抗霉素A时药物氧化受到抑制时，与药物相关的Ca²⁺释放减少。通过注入硫醇氧化剂二酰胺以及叔丁基过氧化氢也可引发Ca²⁺外流。然而，虽然这些化合物引发的Ca²⁺外流在加入硫醇二硫苏糖醇后受到限制，但与药物相关的Ca²⁺外流对硫醇几乎没有敏感性（如果有的话）。加入氯化铵进一步使线粒体中的NADPH氧化，对与药物相关的Ca²⁺外流没有影响。预先加入α - 激动剂去氧肾上腺素可抑制因加入药物而导致的Ca²⁺释放。虽然从肝线粒体和肝细胞中Ca²⁺外流所涉及的分子机制以及调节意义尚不清楚，但从目前的实验可以得出结论，在烟酰胺核苷酸连接的Ca²⁺外流情况下，NADPH的氧化可能就足够了，并不需要NADH的氧化。