Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
Board

Na+ gradient is of major importance in maintaining neuronal viability. Injury mediated escalation of Na+ influx may result in Na+ gradient breakdown with consequent Ca2+ overload and excitotoxicity, due to blockade or reversal of the Na+/Ca2+ exchanger and glutamate transporter. We studied the processes leading to death of isolated rat thalamic neurons overloaded with Na+ during their exposure to Na,K-pump inhibitor ouabain (250 microM), Na-ionophore monensin (50 microM) and Na-channel opener veratridine (50 microM). Neuronal viability was assessed with calcein AM and ethidium homodimer. [Na+]i and [Ca2+]i were monitored using Sodium GreenTM and Calcium OrangeTM. We found that exposure to veratridine or monensin induced cell swelling, rounding and progressive rise in [Na+]i and [Ca2+]i. Fluorescent 9-anthroylouabain binding assay detected that veratridine and monensin exposures results in significant increase in the membrane density of phosphorylated Na,K-pump molecules. Impairment of Na,K-ATPase activity with ouabain during veratridine or monensin exposure resulted in additional increase in [Na+]i and [Ca2+]i, rounding, swelling and massive neuronal death. It is concluded that mammalian central neurons adopt limited capacity for Na-mediated feedback regulation of pump activity which may moderate a rise in internal sodium and delay cell death following persistent increase in Na+ influx. Supported by grants from MRC and Heart and Stroke Foundation of Canada.

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Poster Number PAsenatorov0621
Keywords: cell death, Na, K-pump, sodium, calcium