Nalwaya Nitesh, Deen William M
Department of Chemical Engineering and Biological Engineering Division, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Chem Res Toxicol. 2003 Jul;16(7):920-32. doi: 10.1021/tx025664w.
A mathematical model was developed to predict the intracellular concentrations of NO, O(2)(-), and peroxynitrite in suspension cell cultures exposed to NO and/or peroxynitrite. Oxygen and CO(2) were also considered. Steady state concentrations were computed as a function of radial position within an idealized spherical cell, with a distinction being made between cytosolic and mitochondrial values. Spatial variations in the intracellular concentrations of O(2), CO(2), and NO were found to be negligible. The extremely low membrane permeabilities for O(2)(-) (estimated from lipid bilayer data) caused O(2)(-) to be consumed in the compartment in which it was generated (mitochondria or cytosol) and resulted in concentrations that depended on the generation rate and the concentrations of superoxide dismutase and NO in the individual compartments. Special attention was paid to the origins of intracellular peroxynitrite. Potential sources of peroxynitrite include intracellular generation in mitochondria and cytosol and (depending on the type of experiment) diffusion of extracellular peroxynitrite into the cell. The relative importance of extracellular and intracellular sources was estimated for a wide variety of conditions. The calculated mitochondrial concentrations were generally 5-10 times higher than the cytosolic values, and it was found that mitochondria may act either as sources or sinks for cytosolic peroxynitrite, depending on the experimental conditions. For the baseline conditions, including an NO concentration of 1 microM and no peroxynitrite in the medium, the cytosolic peroxynitrite concentration was estimated as approximately 2 nM. The extracellular peroxynitrite concentration required to double the cytosolic level was approximately 25 nM, and an extracellular concentration of approximately 100 nM was needed to effect a 5-fold increase. For extracellular concentrations smaller than 25 nM, intracellular generation predominated.
建立了一个数学模型，用于预测暴露于一氧化氮（NO）和/或过氧亚硝酸盐的悬浮细胞培养物中NO、超氧阴离子（O₂⁻）和过氧亚硝酸盐的细胞内浓度。同时也考虑了氧气和二氧化碳。稳态浓度作为理想化球形细胞内径向位置的函数进行计算，区分了胞质和线粒体的值。发现细胞内O₂、CO₂和NO浓度的空间变化可忽略不计。O₂⁻极低的膜通透性（根据脂质双分子层数据估算）导致O₂⁻在其产生的隔室（线粒体或胞质溶胶）中被消耗，并导致其浓度取决于各个隔室中的产生速率以及超氧化物歧化酶和NO的浓度。特别关注了细胞内过氧亚硝酸盐的来源。过氧亚硝酸盐的潜在来源包括线粒体和胞质溶胶中的细胞内生成以及（取决于实验类型）细胞外过氧亚硝酸盐扩散到细胞中。在各种条件下估算了细胞外和细胞内来源的相对重要性。计算得出的线粒体浓度通常比胞质值高5至10倍，并且发现线粒体可能根据实验条件充当胞质过氧亚硝酸盐的来源或汇。对于基线条件，包括NO浓度为1微摩尔/升且培养基中无过氧亚硝酸盐，胞质过氧亚硝酸盐浓度估计约为2纳摩尔/升。使胞质水平加倍所需的细胞外过氧亚硝酸盐浓度约为25纳摩尔/升，而要实现5倍增加则需要细胞外浓度约为100纳摩尔/升。对于小于25纳摩尔/升的细胞外浓度，细胞内生成占主导。
