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      Oxidative Stress in a Novel Model of Chronic Acidosis in LLC-PK1 Cells

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          Chronic metabolic acidosis occurs commonly in chronic renal failure (CRF). The proximal renal tubular cell is the site in the kidney of high oxidative metabolic activity and in CRF is associated with adaptive hypertrophy and hypermetabolism. We hypothesised that chronic acidosis may lead to increased generation of reactive oxygen species due to increased oxidative activity. We developed a novel model of chronic acidosis in LLC-PK1 cells and measured markers of oxidative stress and metabolism. Acidosis led to a reduction in cellular total glutathione and protein thiol content and an increase in glutathione peroxidase activity and NH<sub>3</sub> generation. The expression of constitutively expressed heat stress protein (HSP) HSC70 and HSP60 increased at pH 7.0.

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          Heat shock proteins HSP25, HSP60, HSP72, HSP73 in isoosmotic cortex and hyperosmotic medulla of rat kidney.

          The distribution of heat shock proteins (HSP) HSP60, HSP73, HSP72 and HSP25 in the isoosmotic cortex and the hyperosmotic medulla of the rat kidney was investigated using Western blot analysis and immunohistochemistry. HSP73 was homogeneously distributed throughout the whole kidney. The level of HSP60 was high in the renal cortex and low in the medulla. HSP25 and HSP72 were present in large amounts in the medulla. Only low levels of HSP25 and almost undetectable amounts of HSP72 were found in the cortex. HSP25 exists in one nonphosphorylated and several phosphorylated isoforms. Western blot analysis preceded by isoelectric focussing showed that HSP25 predominates in its nonphosphorylated form in the outer medulla but in its phosphorylated form in cortex and inner medulla. Although this intrarenal distribution pattern was not changed during prolonged anaesthesia (thiobutabarbital sodium), a shift from the nonphosphorylated to the phosphorylated isoforms of HSP25 occurred in the medulla. The characteristic intrarenal distribution of the constitutively expressed HSPs (HSP73, HSP60, HSP25) may reflect different states of metabolic activity in the isoosmotic (cortex) and hyperosmotic (medulla) zones of the kidney. The high content of inducible HSP72 in the medulla most likely is a consequence of the osmotic stress imposed upon the cells by the high urea and salt concentrations in the hyperosmotic medullary environment.
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            Free radical activity following contraction-induced injury to the extensor digitorum longus muscles of rats

            The purpose of the study was to investigate the role of free radicals in the injury induced by a protocol of repeated pliometric (lengthening) contractions to the extensor digitorum longus (EDL) muscle in situ in rats. Previous data have indicated that prior treatment with the antioxidant polyethylene glycol-superoxide dismutase reduced the damage that was apparent at 3 days following this type of exercise. Three hours and 3 days following the protocol, the magnitude of the semiquinone-derived free radical signal observed by electron spin resonance spectroscopy (ESR) was not different for exercised and non-exercised skeletal muscles. A reduction in the protein thiol content of muscle was evident at 3 h, and was still apparent at 3 days. Three hours after the protocol, the total muscle glutathione content and the percentage in the oxidized form were unchanged, but by 3 days the percentage of muscle glutathione present in the oxidized form was elevated. The susceptibility of muscle to lipid peroxidation in vitro was reduced 3 days after the pliometric contractions. These data indicate that oxidation of protein thiols and glutathione may be involved in the secondary damage following pliometric contractions, but provide no evidence that the species involved were derived from mitochondrial semiquinone radicals.
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                Author and article information

                Nephron Exp Nephrol
                Cardiorenal Medicine
                S. Karger AG
                September 2003
                17 November 2004
                : 95
                : 1
                : e13-e23
                Departments of aMedicine and bClinical Chemistry, Liverpool University, Liverpool, UK
                73019 Nephron Exp Nephrol 2003;95:e13–e23
                © 2003 S. Karger AG, Basel

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                Page count
                Figures: 7, Tables: 1, References: 43, Pages: 1
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                Original Paper

                Cardiovascular Medicine, Nephrology

                Cell culture, Proximal tubule, Ammonia, Antioxidant enzymes


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