The Journal of Neuroscience, October 11, 2006, 26(41):10430-10437; doi:10.1523/JNEUROSCI.1588-06.2006
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Cellular/Molecular
Intracellular Zinc Elevation Measured with a "Calcium-Specific" Indicator during Ischemia and Reperfusion in Rat Hippocampus: A Question on Calcium Overload
Christian J. Stork and
Yang V. Li
Department of Biomedical Science, Program in Molecular and Cellular Biology, Ohio University, Athens, Ohio 45701
Correspondence should be addressed to Dr. Yang V. Li, Department of Biomedical Sciences, Ohio University, 346 Irvine Hall, Athens, OH 45701. Email: Li{at}oucom.ohiou.edu
Much of our current evidence concerning of the role of calcium (Ca2+) as a second messenger comes from its interaction with fluorescent probes; however, many Ca2+ probes also have a higher affinity for another divalent cation: zinc (Zn2+). In this study, using a selective Zn2+ probe (Newport Green), we investigated the accumulation of intracellular Zn2+ transients in acute rat hippocampal slices during ischemia, simulated by oxygen and glucose deprivation (OGD). Subsequent reperfusion with glucose-containing oxygenated medium resulted in an additional increase in intracellular Zn2+. Such observations compelled us to investigate the contribution of Zn2+ to the alleged intracellular Ca2+ overload occurring in ischemia and reperfusion. Using confocal fluorescent microscopy of Calcium Green-1, a widely used Ca2+ indicator, we detected increases in fluorescence intensity during OGD and reperfusion. However, application of a Zn2+ chelator, at the peak of the fluorescence elevation (interpreted as Ca2+ overload), resulted in a significant drop in intensity, suggesting that rising Zn2+ is the primary source of the increasing Calcium Green-1 fluorescence. Finally, staining with the cell viability indicator propidium iodide revealed that Zn2+ is responsible for the ischemic neuronal cell death, because Zn2+ chelation prevented cells from sustaining ischemic damage. Current cellular models of ischemic injury center on Ca2+-mediated excitotoxicity. Our results indicate that Zn2+ elevation contributes to conventionally recognized Ca2+ overload and also suggest that the role of Ca2+ in neurotoxicity described previously using Ca2+ probes may need to be re-examined to determine whether effect previously attributed to Ca2+ could, in part, be attributable to Zn2+.
Key words: zinc; calcium; fluorescence; ischemia; nitric oxide; cell death
Received April 12, 2006;
revised Aug. 25, 2006;
accepted Aug. 25, 2006.
Correspondence should be addressed to Dr. Yang V. Li, Department of Biomedical Sciences, Ohio University, 346 Irvine Hall, Athens, OH 45701. Email: Li{at}oucom.ohiou.edu
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eLetters:
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- Zinc has not been ignored
- Ian J Reynolds, et al.
- J. Neurosci. Online, 13 Nov 2006
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- A selective calcium indicator is needed. Re: Zinc has not been ignored
- Yang V Li
- J. Neurosci. Online, 28 Jan 2007
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