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  • 1
    Electronic Resource
    Electronic Resource
    Effect of pH on stability of sarcoplasmic reticulum calcium pump in rabbit heart (1993)
    Springer
    Molecular and cellular biochemistry 126 (1993), S. 87-91 
    Details
    ISSN: 1573-4919
    Keywords: ischemia ; acidosis ; oxygen ; free radicals ; myocardium ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The sarcoplasmic reticulum (SR) membranes isolated from rabbit heart were preincubated at pH 6.8 or 7.8 and their Ca2+ pump properties were compared at pH 6.8. The ATP-dependent azide insensitive oxalate-stimulated Ca2+ uptake was reduced more rapidly from the membranes preincubated at 37°C at pH 7.8 than from those preincubated at pH 6.8. The Ca2+−Mg2+-ATPase, and the Ca2+-dependent formation of 110 kDa acylphosphate were also inhibited by the preincubation at the higher pH. Including 1 mM DTT in the preincubation medium reduced the inactivation. The preincubation at 37°C in the presence or absence of DTT caused membranes to become more leaky as the loss of Ca2+ uptake was more rapid than that of ATPase or the acylphosphate formation. The loss of these activities was not accompanied by a breakdown of the protein as monitored in Western blots. It is hypothesized that the SR Ca2+ pump inactivation involves a key-SH group and that the lower pH provides a compensatory protective mechanism for the SR during acidosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01772211
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of peroxide on endothelial nitric oxide synthase in coronary arteries (1998)
    Springer
    Molecular and cellular biochemistry 183 (1998), S. 147-152 
    Details
    ISSN: 1573-4919
    Keywords: free radicals ; ischemia-reperfusion ; endothelium ; smooth muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Reactive oxygen species (ROS) are produced in ischemia and reperfusion. Since endothelial nitric oxide synthase (eNOS) is key to the endothelium- dependent vasodilation, we examined the effects of peroxide on this enzyme. We treated cells cultured from pig coronary artery endothelium with different concentrations of hydrogen peroxide, washed them, solubilized them and measured NOS activity by arginine to citrulline conversion. Hydrogen peroxide inhibited the eNOS activity with an IC50 value of 0.85 ± 0.39 mM. In another experiment, we perfused arteries with solutions containing 0 or 1 mM hydrogen peroxide, washed them, removed the endothelium using a cotton swab, centrifuged and solubilized the endothelium and monitored its NOS activity. Hydrogen peroxide (1 mM) did not affect the NOS activity significantly (p 〉 0.05) in this assay. We conclude that the inactivation of eNOS by hydrogen peroxide does not play a major role in the ischemia- reperfusion damage because the peroxide concentrations attained during ischemia-perfusion are much lower than those affecting the eNOS activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006828205261
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of peroxide on contractility of coronary artery rings of different sizes (1999)
    Springer
    Molecular and cellular biochemistry 194 (1999), S. 159-164 
    Details
    ISSN: 1573-4919
    Keywords: free radicals ; ischemia-reperfusion ; sarcoplasmic reticulum ; Ca2+-Mg2+-ATPase ; calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Reactive oxygen species (ROS, free radicals) produced during cardiac ischemia and reperfusion can damage the contractile functions of arteries. The sarcoplasmic reticulum (SR) Ca2+ pump in coronary artery smooth muscle is very sensitive to ROS. Here we show that contractions of de-endothelialized rings from porcine left coronary artery produced by the hormone Angiotensin II and by the SR Ca2+ pump inhibitors cyclopiazonic acid and thapsigargin correlate negatively with the tissue weight. In contrast, the contractions due to membrane depolarization by high KCl correlate positively. Peroxide also produces a small contraction which correlates negatively with the tissue weight. When artery rings are treated with peroxide and washed, their ability to contract with Angiotensin II, cyclopiazonic acid and thapsigargin decreases. Thus, the SR Ca2+ pump may play a more important role in the contractility of the smaller segments of the coronary artery than in the larger segments. These results are consistent with the hypothesis that ROS which damage the SR Ca2+ pump affect the contractile function of the distal segments more adversely than of the proximal segments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006902603056
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of peroxide on the fluorescence of the Ca2+ probe Fluo 3 and the pH probe BCECF (1998)
    Springer
    Molecular and cellular biochemistry 178 (1998), S. 77-80 
    Details
    ISSN: 1573-4919
    Keywords: free radicals ; ischaemia-reperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Fluorescence probes are invaluable tools in monitoring intracellular ion concentrations. They have also been used for studying how reactive oxygen species alter these concentrations and yet there are no studies indicating how reactive oxygen species directly affect the characteristics of the probes. Our concern was that if reactive oxygen were to affect characteristics of these probes, these measurements would be inconsequential. Therefore, we examined the effects of peroxide on the Ca2+-sensitive dye Fluo 3 and the pH sensitive dye BCECF. Peroxide concentrations below 10 mM did not alter fluorescence or binding characteristics of either dye. Since the concentrations of peroxide used in most pathophysiological experiments are in the micromolar range, we conclude that these probes are appropriate for monitoring the effects of peroxide on intracellular ion concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006867423362
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