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  • 1
    Electronic Resource
    Electronic Resource
    The antioxidant defense system of isolated guinea pig Leydig cells (1993)
    Springer
    Molecular and cellular biochemistry 126 (1993), S. 1-7 
    Details
    ISSN: 1573-4919
    Keywords: Leydig cells ; testes ; superoxide dismutase ; catalase glutathione peroxidase ; glutathione ; hydrogen peroxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Utilization of highly enriched preparations of steroidogenic Leydig cells have proven invaluable for studying the direct effects of various hormones and agents on Leydig cell functionin vitro. However, recent work indicates that isolated Leydig cells are often subjected to oxygen (O2) toxicity when cultured at ambient (19%) oxygen concentrations. Because intracellular antioxidants play an important role in protecting cells against oxygen toxicity, we have investigated the intracellular antioxidant defense system of isolated Leydig cells. The cellular levels of several antioxidants including catalase, glucose-6-phosphate dehydrogenase (G-6-PDH), superoxide dismutase (SOD) of the Cu/Zn & Mn variety, glutathione peroxidase, glutathione reductase and total glutathione were quantitated using enriched populations of Leydig cells isolated from adult male guinea pig testes. Compared to whole testicular homogenates, Leydig cells contained significantly (P〈0.01) less G-6-PDH, total SOD, glutathione reductase and total glutathione, but significantly (P〈0.001) more glutathione peroxidase. Compared to hepatic values previously reported in the guinea pig, Leydig cells contain nearly 400 times less catalase, about 14 times less glutathione peroxidase and almost 11 times less glutathione reductase. Since G-6-PDH and glutathione reductase are both necessary to regenerate reduced gluthathione (GSH) which couples with glutathione peroxidase to breakdown hydrogen peroxide (H2O2) under normal conditions, it is plausible that the oxygen toxicity observed in isolated Leydig cells is due to the intracellular accumulation of H2O2. Using the dichlorofluorescin diacetate (DCF-DA) assay, we found that Leydig cells incubated in the presence of 19% O2 produced significantly (P〈0.001) higher levels of H2O2 with time in culture compared to Leydig cells maintained at 3% O2. These results support the hypothesis that the increased susceptibility of isolated Leydig cells to oxygen toxicity may be due, in part, to decreased amounts of certain antioxidant defenses and an increased production of the reactive oxygen species H2O2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01772202
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of EDTA-chelatable proteins from DNA-protein crosslinks induced by a carcinogenic chromium(VI) in cultured intact human cells (1999)
    Springer
    Molecular and cellular biochemistry 199 (1999), S. 149-162 
    Details
    ISSN: 1573-4919
    Keywords: chromium ; metal carcinogenesis ; DNA-protein crosslink ; two-dimensional gel electrophoresis ; nuclear matrix ; nuclear proteins ; NEPHGE ; X-rays ; oxidant ; MOLT4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract DNA-protein crosslinks (DPCs) were induced in intact human leukemic T-lymphocyte MOLT4 cells or isolated nuclei by treatment with potassium chromate, chromium(III) chloride hexahydrate or x-rays. The proteins complexed to DNA were analyzed by two-dimensional SDS-polyacrylamide gel electrophoresis (PAGE). A group of identical non-histone proteins was crosslinked to DNA by any of the three treatments, except that a 51 kDa basic protein was additionally complexed to DNA when either potassium chromate or chromium(III) chloride hexahydrate was the crosslinking agent. Treatment of chromate-induced DNA-protein crosslinks with EDTA or thiourea followed by ultracentifugation dissociated the major proteins from the complex indicating that these proteins were crosslinked to DNA by direct participation of a EDTA-chelatable form of chromium such as Cr(III) through sulfur containing amino acid residues. The 51 kDa protein was not seen in the post-EDTA pellet but was present in the post-thiourea pellet, indicating that it was also crosslinked to DNA by Cr(III) through non-sulfur-containing amino acids. Digestion of x-rays-induced DPCs by DNase I also revealed this protein on two-dimensional gels indicating that the same protein was also crosslinked by oxidative mechanisms. The involvement of oxidative mechanisms in the crosslinking process was indicated as the majority of the proteins in chromate-induced DPCs were resistant to EDTA and thiourea treatment, and were found to crosslink to DNA when x-rays were used as the crosslinking agent. These results suggest that the chromate-induced DPCs are formed by the generation of reactive oxygen species during the intracellular chromate reduction as well as by the biologically generated Cr(III). About 19% of DNA-protein crosslinks actually involve Cr(III) crosslinking DNA to proteins, about 14% involve Cr(III) crosslinking DNA to proteins through non-sulfhydryl containing moieties and about 5% involve Cr(III) crosslinking DNA to sulfhydryl groups on proteins. The remaining 81% of DNA-protein crosslinks appear to be oxidatively crosslinked out of which about 45% appear to be through sulfhydryl groups and another 36% appear to be through non-sulfhydryl groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006910732307
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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