期刊
FREE RADICAL BIOLOGY AND MEDICINE
卷 34, 期 7, 页码 892-907出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/S0891-5849(03)00025-X
关键词
endothelium; quinone; high-performance liquid chromatography; electron paramagnetic resonance; kinetic model; quinone reductases; transplasma membrane electron transport; free radicals
The pulmonary endothelium is capable of reducing certain redox-active compounds as they pass from the systemic venous to the arterial circulation. This may have important consequences with regard to the pulmonary and systemic disposition and biochemistry of these compounds. Because quinones comprise an important class of redox-active compounds with a range of physiological, toxicological, and pharmacological activities, the objective of the present study was to determine the fate of a model quinone, coenzyme Q(0) (Q), added to the extracellular medium surrounding pulmonary arterial endothelial cells in culture, with particular attention to the effect of the cells on the redox status of Q in the medium. Spectrophotometry, electron paramagnetic resonance (EPR), and high-performance liquid chromatography (HPLC) demonstrated that, when the oxidized form Q is added to the medium surrounding the cells, it is rapidly converted to its quinol form (QH(2)) with a small concentration of semiquinone (Q(.-)) also detectable. The isolation of cell plasma membrane proteins revealed an NADH-Q oxidoreductase located on the outer plasma membrane surface, which apparently participates in the reduction process. In addition, once formed the QH(2) undergoes a cyanide-sensitive oxidation by the cells. Thus, the actual rate of Q reduction by the cells is greater than the net QH(2) output from the cells. (C) 2003 Elsevier Science Inc.
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