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Sodium Feedback Regulation of Na,K-pump Activity in Isolated Rat Thalamic Neurons

Senatorov, V V. (Loeb Research Institute, Ottawa Hospital, Canada)
Stys, P. (Loeb Research Institute, Ottawa Hospital, Canada)
Hu, B. (Loeb Research Institute, Ottawa Hospital, Canada)

Contact Person: Vladimir V Senatorov (vsenatorov@lri.ca)


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

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Senatorov, V V.; Stys, P.; Hu, B.; (1998). Sodium Feedback Regulation of Na,K-pump Activity in Isolated Rat Thalamic Neurons. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Available at URL http://www.mcmaster.ca/inabis98/cellbio/senatorov0621/index.html
© 1998 Author(s) Hold Copyright