Hydroperoxide metabolism in mammalian organs.

Abstract

I. INTRODUCTION AND HISTORICAL BACKGROUND The existence of significant levels of potentially dangerous oxidants in cells and tissues under physiological conditions has frequently been proposed but had previously received little quantitative support. Current approaches to the direct 0031~9333/7%WOOOO~Ol.25

Exercise and oxidative stress: Sources of free radicals and their impact on antioxidant systems

“…Both NADH-ubiquinone reductase and ubiquinone-cytochrome c reductase generate O~ and H202 (6). Because the transition from a twoelectron (NADH and FADH2) to a one-electron (ubiquinone) transfer involves the formation of semiubiquinone (QH~ this segment of the ETC becomes a primary site for O~ production (6).…”

“…A metal-catalyzed Fenton reaction or HaberWeiss reaction between O~ and H202 may give rise to "OH (1). Liver mitochondria is estimated to produce 24 nmol O~ rain per g of tissue; with an active conversion to H202 by SOD, a steady-state O~ concentration of 8x10 .8 M can be derived (6). Heart mitochondria generate 0.3-0.6 nmol/min per mg protein representing 2% of the tissue's total oxygen consumption.…”

“…Thus, higher organisms have developed effective antioxidant systems during the course of evolution (1,6). In general, the cell has adequate antioxidant reserves to cope with the production of ROS under physiological conditions such that these toxic compounds do not accumulate.…”

“…The system consists of antioxidant vitamins (water-soluble ascorbic acid and fat-soluble a-tocopherol and b-carotene), thiol-containing, low-molecular weight compounds, mainly glutathione (GSH), and antioxidant enzymes, such as superoxide dismutase (SOD), GSH peroxidase (GPX), and catalase (CAT). Each of these antioxidants plays a unique role in the cell and complements one another geographically and functionally (6). Furthermore, there is evidence that certain antioxidants, such as GSH, may be involved in interorgan transport (7).…”

Mitochondrial‐Mediated Oxidative Ca 2+ /Calmodulin‐Dependent Kinase II Activation Induces Early Afterdepolarizations in Guinea Pig Cardiomyocytes: An In Silico Study

“…The production of mdROS was modeled as a fraction, or shunt , of electrons from the electron transport chain into the matrix, as previously described 5, 47, 51, 52. Studies have shown that under physiological conditions, up to 2% of the electron flowing the respiratory chain are partially reduced to form the superoxide,53 thus the physiological value of shunt was set as 2%. Pathological shunt was set as 10% or 14% to induce sustained mitochondrial oscillations, which is consistent with our previous computational studies 5, 47, 52.…”