Glutathione disulfide (GSSG) accumulates in cells under an increased oxidant load, which occurs during neurohormonal or metabolic stimulation as well as in many disease states. Elevated GSSG promotes protein S-glutathiolation, a reversible post-translational modification, which can directly alter or regulate protein function. We developed novel strategies for the study of protein S-glutathiolation that involved the simple synthesis of N,N-biotinyl glutathione disulfide (biotin-GSSG). Biotin-GSSG treatment of cells mimics a defined component of oxidative stress, namely a shift in the glutathione redox couple to the oxidized disulfide state. This induces widespread protein S-glutathiolation, which was detected on non-reducing Western blots probed with streptavidin-horseradish peroxidase and imaged using confocal fluorescence microscopy and ExtrAvidin-FITC. S-Glutathiolated proteins were purified using streptavidin-agarose and identified using proteomic methods. We conclude that biotin-GSSG is a useful tool in the investigation of protein S-glutathiolation and offers significant advantages over conventional methods or antibody-based strategies. These novel approaches may find widespread utility in the study of disease or redox signaling models where GSSG accumulation occurs. Molecular & Cellular Proteomics 5:215-225, 2006.

These studies provide evidence for the existence of a maintained sub-sarcolemmal elevation of [Na] in ventricular myocardium; however, this fuzzy-space [Na] did not change immediately after the activation of Na influx via voltage-gated Na channels or throughout the contractile cycle.

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It is generally agreed that an imbalance in ionic homeostasis underlies the generation of ischaemia/ reperfusion injury on cardiac myocytes. The major cause of injury is thought to be an increase in intracellular Ca concentration during the initial reperfusion period caused by reversal of Na/Ca exchange as a result of an increased intracellular Na concentration due to activation of Na/H exchange [1]. At present the exact timing of the increase in Na remains controversial and the possibility that subsarcolemmal accumulation of Na occurs has not been widely explored. We used X-ray microanalysis to investigate the development of subsarcolemmal gradients of Na during ischaemia in isolated blood-perfused rabbit papillary muscle and the effects of HOE642, a specific inhibitor of the cardiac Na/H exchanger on Na accumulation.Adult male NZW rabbits were anaesthetised, the hearts were removed and the isolated bloodperfused papillary muscle prepared. The muscle was perfused for a 60 minute stabilization period and then subjected to zero-flow ischaemia for up to 30 minutes. When the effects of HOE642 were investigated the drug was administered for 15 mins before the development of ischaemia. Muscles were cryofixed at the end of diastole using an automatic cryosnapper device [2]. Cryosections were cut at -120°C using a RMC cryoultramicrotome, collected onto Pioloform-coated Ni grids, freezedried overnight and coated with carbon before analysis. Spectra were collected for 50 s live time and analysed in the spot mode using a Zeiss STEM and processed using PGT software. Spectra were taken at distances of 50, 100, 200, 300,400, 500 and 1000 nm from the sarcolemma, and at the cell centre.Under control conditions at the end of diastole a subsarcolemmal gradient of sodium concentrations was observed within the first 200 nm of the sarcolemma. After 20 mins ischaemia the concentrations of Na in the subsarcolemmal region increased, and the gradient extended further into the cell. These changes in ischaemia were abolished when the muscles were pre-incubated with HOE642. Our studies support the concept that intracellular Na concentration is increased during ischaemia as a result of Na/H activation and give the additional information that this increase is, at first, confined to the subsarcolemmal region. References[1] M. Karazyn et al., Circ. Res. 85 (1999) 777 [2] M.J. Shattock et al. J Micrsc. 192 (1998) 269. [3] This work was supported by the Wellcome Trust 446 CD