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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 121 (1993), S. 127-133 
    ISSN: 1573-4919
    Keywords: calcium transport ; nicotinamide-adenine dinucleotides ; rat liver nuclei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of nicotinamide-adenine dinucleotides (NAD+ and NADP+) on Ca2+ transport in rat liver nuclei was investigated. Ca2+ uptake and release were determined with a Ca2+ electrode. Ca2+ uptake was dependent on adenosine triphosphate (ATP; 2mM). The presence of NAD+ (2mM) or NADP+ (1 and 2mM) caused a significant inhibition of Ca2+ uptake following addition of 2mM ATP. Ca2+, which accumulated in the nuclei during 6 min after ATP addition, was significantly released by the addition of NAD+ (0.5–2mM) or NADP+ (0.1–2mM). However, the effect of NADH (2mM) or NADPH (2mM) on Ca2+ uptake and release clearly weakened in comparison with the effects of NAD+ and NADP+. Meanwhile, ryanodine (10μM), thapsigargin (10μM) or oxalate (0.5mM) had no effect on Ca2+ uptake and release in rat liver nuclei. These reagents did not significantly alter the effects of 2mM NAD+ on Ca2+ uptake and release. Thus, NAD+ and NADP+ had a potent effect on Ca2+ transport in rat liver nuclei. The present findings suggest that the liver cytosolic NAD+ (NADP+) is a factor in the regulation of the nuclear Ca2+ concentration. (Mol Cell Biochem121: 127–133, 1993)
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 113 (1992), S. 63-70 
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; calcium transport ; rat liver nuclei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on Ca2+ transport in rat liver nuclei was investigated. Ca2+ uptake and release were determined with a Ca2+ electrode. Ca2+ uptake increased dependent on adenosine triphosphate (ATP; 0.5-2.0 mM), while the uptake was negligible in the presence of 2 mM ADP or AMP. Regucalcin (0.5–2.0 μM) had no effect on Ca2+ uptake following addition of 2.0 mM ATP. Meanwhile, Ca2+, which accumulated in the nuclei during 10 min after ATP addition, was significantly released by the addition of regucalcin. This release was dose-dependent (0.1–2.0 μM). Vanadate (100 μM) and guanosine triphosphate (100 μM) did not cause a significant release of Ca2+ from the nuclei. Trifluoroperazine (TFP; 50 μM), an antagonist of calmodulin, significantly increased Ca2+ release from the nuclei. The presence of regucalcin (0.5 μM) further enhanced the TFP effect. These results indicate that regucalcin stimulates Ca2+ release from liver nuclei, and that the effect is not influenced by calmodulin antagonist. The finding suggests that regucalcin can regulate the Ca2+ transport system in rat liver nuclei.
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  • 3
    ISSN: 1573-4919
    Keywords: calcium ; calcium transport ; brain ; calcium-regulating hormone ; calcium-antagonist ; energy dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The characterization of calcium accumulation in the brain of rats administered orally calcium chloride solution was investigated. Rats received a single oral administration of calcium (15–50 mg/100 g body weight), and they were sacrificed by bleeding-between 15 and 120 min after the administration. The administration of calcium (50 mg/100 g) produced a significant increase in serum calcium concentration and a corresponding elevation of brain calcium content, indicating that the transport of calcium into the brain is associated with the elevation of serum calcium levels. The increase in brain calcium content by calcium administration was not appreciably altered by the pretreatment with Ca2+ channel blockers (verapamil or diltiazem with the doses of 1.5 and 3.0 mg/100 g). In thyroparathyroidectomized rats, the administration of calcium (50 mg/100 g) caused a significant increase in brain calcium content, indicating that calcium-regulating hormones do not participate in the brain calcium transport. Now, brain calcium content was clearly elevated by fasting (overnight), although serum calcium level was not significantly altered. Calcium administration to fasted rats induced a further elevation of brain calcium content as compared with that of control (fasted) rats. The fasting-induced increase in brain calcium content was appreciably restored by refeeding. This restoration was also seen by the oral administration of glucose (0.4 g/100 g) to fasted rats. The present study demonstrates that serum calcium is transported to brain, and that the increased brain calcium is released promptly. The release of calcium from brain may be involved in energy metabolism, and this release may be weakened by the reduction of glucose supply into brain. The finding suggests a physiological significance of energy-dependent mechanism in the regulation of brain calcium.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 125 (1993), S. 43-49 
    ISSN: 1573-4919
    Keywords: Ca2+-ATPase ; calcium transport ; calmodulin ; rat liver nuclei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The role of Ca2+-stimulated adenosine 5′-triphosphatase (Ca2+-ATPase) in Ca2+ sequestering of rat liver nuclei was investigated. Ca2+-ATPase activity was calculated by subtracting Mg2+-ATPase activity from (Ca2+−Mg2+)-ATPase activity. Ca2+ uptake and release were determined with a Ca2+ electrode. Nuclear Ca2+-ATPase activity increased linearly in the range of 10–40 μM Ca2+ addition. With those concentrations, Ca2+ was completely taken up by the nuclei dependently on ATP (2 mM). Nuclear Ca2+-ATPase activity was decreased significantly by the presence of arachidonic acid (25 and 50 μM), nicotinamide-adenine dinucleotide (NAD+; 2 mM) and zinc sulfate (2.5 and 5.0 μM). These reagents caused a significant decrease in the nuclear Ca2+ uptake and a corresponding elevation in Ca2+ release from the nuclei. Moreover, calmodulin (10 μg/ml) increased significantly nuclear Ca2+-ATPase activity, and this increase was not seen in the presence of trifluoperazine (10 μM), an antogonist of calmodulin. The present findings suggest that Ca2+-ATPase plays a role in Ca2+ sequestering by rat liver nuclei, and that calmodulin is an activator. Moreover, the inhibition of Ca2+-ATPase may evoke Ca2+ release from the Ca2+-loaded nuclei.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 148 (1995), S. 33-37 
    ISSN: 1573-4919
    Keywords: DNA fragmentation ; Ca2+-ATPase ; calcium transport ; rat liver nuclei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of nuclear Ca2+ uptake inhibitors on the Ca2+-activated DNA fragmentation in rat liver nuclei was investigated. The addition of Ca2+ (40 μM) into the reaction mixture containing liver nuclei in the presence of 2.0 mM ATP caused a remarkable increase in nuclear DNA fragmentation. This Ca2+-activated DNA fragmentation was not seen in the absence of ATP, because nuclear Ca2+ uptake is not initiated without ATP addition. Moreover, the presence of various reagents (10 μM arachidonic acid, 2.0 mM NAD+, 10 μM zinc sulfate and 0.2 mM N-ethylmaleimide), which could inhibit Ca2+-ATPase activity and Ca2+ uptake in the nuclei, produced a significant inhibition of the Ca2+-activated DNA fragmentation in the nuclei. The results show that the Ca2+-activated DNA fragmentation is involved in the uptake of Ca2+ by the nuclei, suggesting a role of Ca2+ transport system in the regulation of liver nuclear functions.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 166 (1997), S. 183-189 
    ISSN: 1573-4919
    Keywords: calcium transport ; DNA topoisomerase II inhibitor ; apoptosis ; DNA fragmentation ; rat liver nuclei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of various inhibitors of DNA topoisomerase II, which has been shown to induce apoptotic cell death, on Ca2+ transport in isolated rat liver nuclei was investigated. Ca2+ uptake and release were determined with a Ca2+ electrode. The presence of aurintricarboxylic acid (ATA; 10-6 to 10-4 M), etoposide (10-4 M), genistein (10-5 and 10-4 M) or amsacrine (10-4 M) in the reaction mixture caused a significant increase in Ca2+ release from the nuclei. Also, these compounds (10-4 M) significantly inhibited Ca2+ uptake by the nuclei. However, the presence of ATA (10-5 and 10-4 M) in the enzyme reaction mixture did not significantly inhibit Ca2+-ATPase activity, which is involved in the nuclear Ca2+ uptake, in the liver nuclei, while etoposide (10-4 M), genistein (10-4 M) and amsacrine (10-4 M) appreciably decreased the enzyme activity. Meanwhile, addition of Ca2+ clearly activated DNA fragmentation in the liver nuclei. The Ca2+ activated DNA fragmentation was significantly prevented by the presence of etoposide, genistein and amsacrine with the concentrations of 10-5 and 10-4 M in the reaction mixture, although ATA (10-5 and 10-4 M) had no effect. The present study demonstrates that some apoptosis inducible compounds used can influence on Ca2+ transport system in isolated rat liver nuclei, suggesting a decrease of nuclear Ca2+ level involved in nuclear functions. (Mol Cell Biochem 166: 183-189, 1997)
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