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ANESTHETIC PHARMACOLOGY

Propofol Protection of Sodium-Hydrogen Exchange Activity Sustains Glutamate Uptake During Oxidative Stress

Rina Daskalopoulos, BSc^*, Jasminka Korcok, BSc^*, Parviz Farhangkhgoee, DVM, Morris Karmazyn, PhD, Adrian W. Gelb, MB, and John X. Wilson, PhD^*

Departments of *Physiology, Pharmacology and Toxicology, and Anaesthesia, University of Western Ontario, London, Ontario, Canada

Address correspondence and reprint requests to Dr. John X. Wilson, Department of Physiology, University of Western Ontario, London, Ontario, N6A 5C1, Canada. Address e-mail to John.Wilson{at}fmd.uwo.ca

	Abstract

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We investigated the role of intracellular pH in protection by propofol of glutamate uptake during oxidative stress. Exposure of primary astrocyte cultures to tert-butylhydroperoxide (t-BOOH, 300 µM) decreased the initial rate of Na-dependent glutamate uptake. Either propofol or -tocopherol, administered 30 min after t-BOOH, attenuated this transport inhibition. These lipophilic antioxidants protected glutamate uptake whether the medium contained 25 mM bicarbonate or was nominally bicarbonate-free. t-BOOH also inhibited Na/H exchanger isoform 1 (NHE1) activation by intracellular protons and propofol prevented this inhibition. Blockade of NHE1 by the potent antagonist, 5-(N-ethyl-N-isopropyl) amiloride (1 µM), abolished the protective effects of small concentrations of propofol (1 µM) and -tocopherol (40 µM) on glutamate uptake during oxidative stress in bicarbonate-free medium. 5-(N-ethyl-N-isopropyl) amiloride had no effect on antioxidant rescue of glutamate transport in medium containing 25 mM bicarbonate. These results indicate that regulation of intracellular pH may contribute to neuroprotection by propofol and other lipophilic antioxidants. Propofol concentrations that are associated with anesthesia and neuroprotection may prevent intracellular acidification during oxidative stress by preserving the NHE1 response to cytosolic protons. However, if intracellular acidification occurs nonetheless, then propofol protection of glutamate uptake activity becomes less effective and the extracellular glutamate concentration may increase to neurotoxic levels.

IMPLICATIONS: Anesthetic concentrations of propofol maintain the capacity of brain cells to extrude protons during oxidative stress. However, if intracellular acidification occurs nonetheless, then propofol’s protection of glutamate clearance mechanisms from oxidative damage becomes attenuated, and extracellular glutamate concentration may increase to neurotoxic levels.

	Introduction

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Pharmacologic protection of neurons during regional ischemia continues to be a sought after goal of neuroanesthesiologists. Drugs that act on astrocytes may be useful for this purpose, particularly because these nonneuronal cells clear the excitatory transmitter, glutamate, from the brain’s extracellular fluid. Glutamate is removed from synaptic spaces by high-affinity, Na- and proton-dependent transporters (EAAT1 and EAAT2) located on astrocytes (1). During ischemia-reperfusion, reactive oxygen species impair this clearance mechanism (1) and the extracellular glutamate concentration increases to excitotoxic levels that kill neurons and expand infarct volume (2). Astrocytes undergo intracellular acidification during ischemia-reperfusion in situ (3) or exposure to oxidative stress in vitro (4). Acidification of intracellular pH (pH_i) to values <7.0 inhibits astrocytic glutamate uptake (5) and pH_i <6.5 increases infarct volume (6).

Propofol (2,6-diisopropylphenol) is an IV anesthetic and sedative that dose-dependently increases the survival of brain cells and enhances neurologic outcome in experimental stroke (7–9). Propofol’s structure differs from other hypnotic sedatives, but resembles the native antioxidant -tocopherol (vitamin E), in containing a phenolic hydroxyl group. This moiety scavenges free radicals and inhibits lipid peroxidation (10–13). We have shown that propofol restores glutamate transport rate in astrocytes that have been oxidatively stressed by tert-butylhydroperoxide (t-BOOH) (a cell-permeant alkyl peroxide that causes lipid peroxidation) (14). Virtually complete protection of glutamate transport activity was achieved when 8 µM propofol was administered simultaneously with t-BOOH and partial protection was observed when propofol was delayed 30 min after t-BOOH (15).

The Na/H exchanger isoform 1 (NHE1), Na/HCO₃ cotransporter, and Cl/HCO₃ exchanger are the predominant transporters regulating pH_i in astrocytes (Fig. 1) (3,15–18). Protons accumulating in cytosol interact with a sensor site of NHE1 to promote exchange of protons for Na across the plasma membrane. NHE1 is evidently important for brain function, because NHE1-deficient mice develop ataxia and epilepsy (19,20). NHE1 activity can be blocked selectively with amiloride analogs, such as 5-(N-ethyl-N-isopropyl) amiloride (EIPA). EIPA abolishes the recovery of pH_i from an acid load when astrocytes are incubated in bicarbonate-free medium but not in medium containing a physiologic concentration of bicarbonate (16).

View larger version (17K): [in this window] [in a new window]   Figure 1. Diagram of the astrocyte showing the principal sites of action for the drugs used in this study. Glutamate is transported via excitatory amino acid transporters (EAAT). NHE1 is the Na/H exchanger inhibited by 5-(N-ethyl-N-isopropyl) amiloride (EIPA). The Na/HCO3 cotransporter (NBC) and the Cl/HCO3 exchanger are bicarbonate transporters that, along with NHE, are responsible for intracellular pH regulation (17).

	Materials and Methods

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L-[³H]Glutamic acid (38–46 Ci/mmol) was purchased from Amersham Canada (Oakville, Ontario, Canada). 2',7'-Biscarboxyethyl carboxyfluorescein (BCECF) acetoxymethyl ester was from Molecular Probes (Eugene, OR). -Tocopherol, t-BOOH, EIPA, and L-glutamate were purchased from Sigma Chemical Company (St. Louis, MO). Horse serum was obtained from Gibco Laboratories (Burlington, Ontario, Canada). Propofol was purchased from Aldrich Chemical Company (Oakville, Ontario, Canada). Propofol and -tocopherol were dissolved in ethanol, whereas EIPA was dissolved in dimethylsulfoxide (DMSO). Control cultures received the same concentration of each vehicle (ethanol 3 µL/mL or DMSO 0.2 µL/mL) as did the drug-treated cultures.

Cell Cultures
The experimental protocol was approved by the University of Western Ontario Council on Animal Care. Primary astrocyte cultures of the neopallium of 1-day-old Wistar rats were prepared according to our published procedure (14,17). These cultures were on coverslips for experiments measuring pH_i and were in 60-mm dishes for all other experiments. Cultures were grown in horse serum-supplemented, minimum essential medium. They reached confluence after 2 wk and were used for experiments after 16–21 days in vitro. Immunocytochemical analysis showed that these cultures were nearly homogeneous for cells that expressed the astrocytic markers glial fibrillary acidic protein and connexin43 gap junction protein. In contrast, very few cells expressed neuronal (<0.1% of cells reacted with an antibody specific for microtubule-associated protein 2) or microglial (<1% of cells reacted with anti-CD68 or anti-HLADR antibodies) markers. Thus, nearly all of the cultured cells were astrocytes and the experimental results obtained with them reflected astrocytic functions.

Experimental Procedures
Temperature was maintained at 37°C for all incubations. Confluent primary astrocytes were incubated for 3 h in serum-free minimum essential medium (pH 7.3, equilibrated with 5% CO₂ and 95% air). Subsequently, the cells were incubated with EIPA (1 µM) or DMSO vehicle (0.2 µL/mL) in nominally bicarbonate-free transport medium (containing, in mM, 134 NaCl, 5.2 KCl, 1.8 CaCl2, 0.8 MgSO4, 10 glucose, and 20 HEPES; 300 mOsm; pH 7.3; equilibrated with air). After 30 min, t-BOOH (300 µM) or aqueous vehicle (1 µL/mL) was added. After another 30 min, the cells were washed and incubated for a final 30 min in medium that did not contain t-BOOH but did contain ethanol vehicle, vitamin E (40–200 µM) or propofol (1–8 µM). These concentrations of propofol are similar to the levels of free anesthetic (i.e., not bound to proteins) that are achieved during anesthesia [see the discussion of anesthetic and neuroprotective concentrations of propofol in Ref. (15)]. EIPA treatment was continued during this final 30-min incubation for those cultures that had begun receiving it earlier, so that the total duration of EIPA exposure was 90 min. In parallel experiments, the above procedures were repeated using transport medium containing 25 mM bicarbonate equilibrated with 5% CO₂ and 95% air.

The initial rate of Na-dependent glutamate uptake (100 µM, 10 mCi/mmol, 1 min) was measured for astrocytes in 60-mm culture dishes according to the procedure we described previously (14). The radioactive cell contents and media aliquots were analyzed by liquid scintillation counting. Uptake rates were expressed per gram cell protein, which was measured by the Lowry method. Experiments in which t-BOOH decreased glutamate uptake by <50% were excluded from further analysis. Na-glutamate cotransport rates were calculated as the difference between total and Na-independent (N-methyl-D-glucamine substituted for Na as the principal cation in the medium) rates of glutamate uptake. Intracellular GSH concentration was determined by a published method (14).

For measurement of Na/H exchange rate, primary astrocytes on coverslips were incubated with BCECF-acetoxymethyl ester (5 µg/mL) under serum-free conditions, as described by Dixon and Wilson (17). Microscopic examination confirmed that predominantly cytosolic loading of the pH-sensitive probe, BCECF, was achieved. pH_i was monitored continuously at excitation wavelengths of 440 nm and 490 nm with emission wavelength of 530 nm. NHE1 activity was determined by measuring the rate of pH_i recovery after acute acid loading by the ammonium chloride prepulse method. The fluorescence ratio was calibrated for each cell culture by using nigericin and an appropriate range of extracellular pH, as we described previously (17).

Numerical data were expressed as the mean ± SEM values for n number of experiments with triplicate replications. Analysis of variance with the Tukey-Kramer multiple comparison test or Student’s paired t-test (two-tailed) was used to evaluate the effects of treatments. A P value < 0.05 was considered significant.

	Results

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The principal cellular sites of action for the drugs used in this study are indicated in Figure 1. We observed that in nominally bicarbonate-free medium, oxidative stress of primary astrocyte cultures by the cell-permeant initiator of lipid peroxidation, t-BOOH (300 µM for 30 min, followed by a 30-min washout period), decreased the initial rate of Na-dependent glutamate uptake (Fig. 2). The NHE antagonist EIPA (1 µM, 90 min) did not alter glutamate uptake in control or t-BOOH astrocytes. Delayed administration of 1–8 µM propofol, during the 30-min washout period, attenuated the inhibitory effect of t-BOOH. However, 1 µM EIPA (Fig. 2) abolished protection of glutamate transport by 1 µM propofol. Increasing the propofol concentration to 8 µM overcame this injurious effect of EIPA (Fig. 2). Like propofol, delayed administration of vitamin E during the 30-min washout period was observed to rescue astrocyte glutamate transport from t-BOOH-induced inhibition (Fig. 3). EIPA (1 µM) abolished this protection for 40 µM vitamin E but not for 200 µM vitamin E.

View larger version (27K): [in this window] [in a new window]   Figure 2. Inhibition of Na/H exchange (NHE) interferes with propofol (PPF) rescue of glutamate uptake in oxidatively stressed astrocytes. Primary astrocyte cultures were incubated in bicarbonate-free medium with the NHE antagonist 5-(N-ethyl-N-isopropyl) amiloride (EIPA) (1 µM) or its vehicle (dimethylsulfoxide) before (30 min) and during a 30-min exposure to tert-butylhydroperoxide (t-BOOH) (300 µM) or aqueous vehicle. Subsequently, t-BOOH was removed and the cultures were incubated for 30 min in medium containing PPF (1–8 µM), EIPA, or vehicle. Finally, the initial rate of glutamate uptake (100 µM, 1 min) was measured. Plotted are the mean ± SEM values for n = 3–11 experiments with triplicate replications in each. *P < 0.05 for PPF rescue from t-BOOH injury. #P < 0.05 for the effect of EIPA.

View larger version (23K): [in this window] [in a new window]   Figure 3. Inhibition of Na/H exchange interferes with vitamin E rescue of glutamate uptake in oxidatively stressed astrocytes. The procedure was the same as described in Figure 2 except that vitamin E (40–200 µM) was substituted for propofol. Plotted are the mean ± SEM values for n = 4 experiments with triplicate replications in each. *P < 0.05 for vitamin E rescue from tert-butylhydroperoxide (t-BOOH) injury. #P < 0.05 for the effect of 5-(N-ethyl-N-isopropyl) amiloride (EIPA).

View larger version (26K): [in this window] [in a new window]   Figure 4. 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and propofol (PPF) do not affect intracellular glutathione (GSH) concentration in oxidatively stressed astrocytes. The procedure was the same as described in Figure 2 except that the cells were harvested for measurement of GSH concentration. Plotted are the mean ± SEM values for n = 4 experiments. *P < 0.05 for effect of tert-butylhydroperoxide (t-BOOH).

View larger version (28K): [in this window] [in a new window]   Figure 5. Effect of bicarbonate on glutamate uptake by astrocytes incubated with 5-(N-ethyl-N-isopropyl) amiloride (EIPA), tert-butylhydroperoxide (t-BOOH), and propofol (PPF). The procedure was the same as described in Figure 2 except that the medium contained CO2:HCO3-. Plotted are the mean ± SEM values for n = 6 experiments with triplicate replications in each. *P < 0.05 for PPF rescue from t-BOOH injury. #P < 0.05 for the effect of CO2:HCO3-.

View larger version (14K): [in this window] [in a new window]   Figure 6. Effects of 5-(N-ethyl-N-isopropyl) amiloride (EIPA), tert-butylhydroperoxide (t-BOOH), and propofol (PPF) on recovery of intracellular pH (pHi) from an acid load. Rat primary astrocytes were perfused with 2',7'-biscarboxyethyl carboxyfluorescein (BCECF) acetoxymethyl ester and either EIPA (1 µM) or its vehicle (dimethylsulfoxide) for 30 min in bicarbonate-free medium (37°C). The cells were then perfused with medium containing ammonium chloride (25 mM). Subsequent perfusion with NH4+-free medium induced a rapid loss of intracellular NH3 that acidified pHi acutely and activated Na/H exchanger isoform 1. t-BOOH (300 µM), propofol (8 µM), or the latter’s vehicle (ethanol) were present for 10 min before NH4+, during the 5-min exposure to NH4+, and throughout the 12-min period of NH4+ washout. pHi was monitored by measuring the ratio of BCECF fluorescence at 440 and 490 nm. Shown are representative records for the 12-min period after NH4+ removal.

	Discussion

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We investigated for the first time the role of pH_i in propofol protection of high-affinity glutamate uptake. To the clinician, this line of investigation is important because failure of the glutamate uptake system to clear glutamate from the extracellular fluid leads to excitotoxic killing of neurons (1,2). Glutamate clearance is mediated principally by astrocytes but these cells are compromised by the oxidative stress that accompanies ischemia and reperfusion. Oxidative stress in astrocytes depletes adenosine triphosphate (ATP), inhibits Na,K-adenosine triphosphatase, and increases intracellular levels of both Na and protons (4). The present study indicates that clinical concentrations of propofol prevent inhibition by oxidants of glutamate uptake into astrocytes, whether or not a physiologic level of bicarbonate is present. This effect of propofol may accelerate clearance of the transmitter from synaptic clefts and thereby prevent excitotoxic killing of neurons. The same effect was also seen with vitamin E, which is an endogenous scavenger of lipophilic radicals and inhibitor of lipid peroxidation in membranes. The qualitatively similar improvement in cell function achieved by propofol and vitamin E is consistent with measurements of lipid peroxidation in isolated membranes showing that propofol can replace the vitamin as an antioxidant (10,13). Propofol does not prevent t-BOOH-induced GSH depletion (14). These findings are consistent with the view that propofol’s antioxidant effect, like that of vitamin E, occurs in membranes and not in the aqueous phase of intact cells.

Blockade of Na/H exchange by EIPA was not protective itself and interfered with propofol rescue under bicarbonate-free conditions. In bicarbonate medium, EIPA had no effect on propofol rescue of glutamate transport from peroxyl inhibition. This result suggests EIPA only inhibits glutamate uptake in oxidatively stressed cells if they cannot use bicarbonate to regulate pH_i. The transmembrane gradient of protons is important for high-affinity glutamate uptake because the influx of glutamate through EAAT1 and EAAT2 requires the cotransport of protons as well as Na (1). In astrocytes incubated with t-BOOH and propofol under bicarbonate-free conditions, EIPA-sensitive NHE1 activity keeps the intracellular concentration of protons small enough to avoid impairment of glutamate uptake.

Although we did not observe protection of glutamate uptake by EIPA, NHE1 antagonists may increase the brain’s resistance to ischemia-reperfusion injury by attenuating extracellular acidification, endothelial cell swelling, and neutrophil activation (21–24). We found that increasing the propofol concentration overcame the deleterious effect of EIPA on glutamate uptake in oxidatively stressed astrocytes. Similarly, neurologic outcome after cerebral ischemia-reperfusion in rats is superior with large-dose propofol than with smaller doses (8).

NHE1-mediated Na/H exchange can be activated by intracellular acidification in astrocytes that have not been oxidatively stressed (3,15–18), but the response of NHE1 to acid loading is decreased acutely in cells exposed to t-BOOH and other oxidants [Refs. (25–27) and present experiments]. A novel finding of our study is that propofol maintains the response of NHE1 to acid loading during oxidative stress and may thereby mitigate intracellular acidification.

Propofol may act through several mechanisms to preserve NHE1 activity in cells exposed to t-BOOH. First, propofol inhibits lipid peroxidation, with concentrations as small as 2 µM having been found effective in microsomal suspensions containing GSH (10,11). Second, astrocytic NHE1 activity is dependent on intracellular ATP (18) and propofol may prevent ATP depletion by t-BOOH. Third, propofol’s blockade of Na channels (28) and maintenance of Na,K-adenosine triphosphatase activity may prevent cytosolic Na concentration from increasing to levels that inhibit NHE1. Finally, propofol may modulate regulator sites in NHE1 and thereby activate Na-H exchange.

In conclusion, the present study is consistent with the view that regulation of pH_i contributes to neuroprotection by the lipophilic antioxidants, propofol, and vitamin E. Propofol concentrations associated with anesthesia and neuroprotection prevented t-BOOH-induced inhibition of pH_i recovery by astrocytes after an acid load. This finding suggests that propofol prevents intracellular acidification during oxidative stress by preserving NHE1 responsiveness to cytosolic protons. However, if intracellular acidification occurs nonetheless, then protection of high-affinity glutamate uptake activity by lipophilic antioxidants becomes attenuated and extracellular glutamate concentration may increase to neurotoxic levels.

	Acknowledgments

 
The assistance of Ewa Jaworski in preparing cell cultures is gratefully acknowledged.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Trotti D, Danbolt NC, Volterra A. Glutamate transporters are oxidant-vulnerable: a molecular link between oxidative and excitotoxic neurodegeneration? Trends Pharmacol Sci 1998; 19: 328–34.[Medline]
2. Yan YP, Yin KJ, Sun FY. Effect of glutamate transporter on neuronal damage induced by photochemical thrombotic brain ischemia. Neuroreport 1998; 9: 441–6.[Web of Science][Medline]
3. Lascola C, Kraig RP. Astroglial acid-base dynamics in hyperglycemic and normoglycemic global ischemia. Neurosci Biobehav Rev 1997; 21: 143–50.[Web of Science][Medline]
4. Tsai KL, Wang SM, Chen CC, et al. Mechanism of oxidative stress-induced intracellular acidosis in rat cerebellar astrocytes and C6 glioma cells. J Physiol 1997; 502: 161–74.[Abstract/Free Full Text]
5. Swanson RA, Farrell K, Simon RP. Acidosis causes failure of astrocyte glutamate uptake during hypoxia. J Cereb Blood Flow Metab 1995; 15: 417–24.[Web of Science][Medline]
6. Simon RP, Niro M, Gwinn R. Brain acidosis induced by hypercarbic ventilation attenuates focal ischemic injury. J Pharmacol Exp Ther 1993; 267: 1428–31.[Abstract/Free Full Text]
7. Kochs E, Hoffman WE, Werner C, et al. The effects of propofol on brain electrical activity, neurologic outcome, and neuronal damage following incomplete ischemia in rats. Anesthesiology 1992; 76: 245–52.[Web of Science][Medline]
8. Yamasaki T, Nakakimura K, Matsumoto M, et al. Effects of graded suppression of the EEG with propofol on the neurological outcome following incomplete cerebral ischaemia in rats. Eur J Anaesthesiol 1999; 16: 320–9.[Web of Science][Medline]
9. Young Y, Menon DK, Tisavipat N, et al. Propofol neuroprotection in a rat model of ischaemia reperfusion injury. Eur J Anaesthesiol 1997; 14: 320–6.[Web of Science][Medline]
10. Aarts L, van der Hee R, Dekker I, et al. The widely used anesthetic agent propofol can replace alpha-tocopherol as an antioxidant. FEBS Lett 1995; 357: 83–5.[Web of Science][Medline]
11. Bao YP, Williamson G, Tew D, et al. Antioxidant effects of propofol in human hepatic microsomes: concentration effects and clinical relevance. Br J Anaesth 1998; 81: 584–9.[Abstract/Free Full Text]
12. Chen H, Chiang M, Wang C, et al. Inhibition of tert-butyl hydroperoxide-induced cell membrane bleb formation by alpha-tocopherol and glutathione. Food Chem Toxicol 2000; 38: 1089–96.[Web of Science][Medline]
13. Hans P, Deby C, Deby-Dupont G, et al. Effect of propofol on in vitro lipid peroxidation induced by different free radical generating systems: a comparison with vitamin E. J Neurosurg Anesth 1996; 8: 154–8.[Web of Science][Medline]
14. Sitar SM, Hanifi-Moghaddam P, Gelb A, et al. Propofol prevents peroxide-induced inhibition of glutamate transport in cultured astrocytes. Anesthesiology 1999; 90: 1446–53.[Web of Science][Medline]
15. Peters CE, Korcok J, Gelb AW, Wilson JX. Anesthetic concentrations of propofol protect against oxidative stress in primary astrocyte cultures: comparison with hypothermia. Anesthesiology 2001; 94: 313–21.[Web of Science][Medline]
16. Bevensee MO, Weed RA, Boron WF. Intracellular pH regulation in cultured astrocytes from rat hippocampus. I. Role of HCO₃^-. J Gen Physiol 1997; 110: 453–65.[Abstract/Free Full Text]
17. Dixon SJ, Wilson JX. Fluorescence measurement of cytosolic pH in cultured rodent astrocytes. Methods Neurosci 1995; 27: 196–213.
18. Shrode LD, Klein JD, O’Neill WC, et al. Shrinkage-induced activation of Na⁺/H⁺ exchange in primary rat astrocytes: role of myosin light-chain kinase. Am J Physiol 1995; 269: C257–66.[Abstract/Free Full Text]
19. Bell SM, Schreiner CM, Schultheis PJ, et al. Targeted disruption of the murine Nhe1 locus induces ataxia, growth retardation, and seizures. Am J Physiol 1999; 276: C788–95.
20. Cox GA, Lutz CM, Yang CL, et al. Sodium/hydrogen exchanger gene defect in slow-wave epilepsy mutant mice. Cell 1997; 91: 139–48.[Web of Science][Medline]
21. Phillis JW, Estevez AY, Guyot LL, et al. 5-(N-Ethyl-N-isopropyl)-amiloride, an Na⁺-H⁺ exchange inhibitor, protects gerbil hippocampal neurons from ischemic injury. Brain Res 1999; 839: 199–202.[Web of Science][Medline]
22. Gumina RJ, Auchampach J, Wang R, et al. Na⁺/H⁺ exchange inhibition-induced cardioprotection in dogs: effects on neutrophils versus cardiomyocytes. Am J Physiol 2000; 279: H1563–70.[Abstract/Free Full Text]
23. Kempski O, Behmanesh S. Endothelial cell swelling and brain perfusion. J Trauma 1997; 42: S38–40.[Web of Science][Medline]
24. Lauro KL, Kabert H, LaManna JC. Methyl isobutyl amiloride alters regional brain reperfusion after resuscitation from cardiac arrest in rats. Brain Res 1999; 831: 64–71.[Web of Science][Medline]
25. Cutaia M, Parks N. Oxidant stress decreases Na⁺/H⁺ antiport activity in bovine pulmonary artery endothelial cells. Am J Physiol 1994; 267: L649–59.[Abstract/Free Full Text]
26. Hu Q, Xia Y, Corda S, et al. Hydrogen peroxide decreases pH_i in human aortic endothelial cells by inhibiting Na⁺/H⁺ exchange. Circ Res 1998; 83: 644–51.[Abstract/Free Full Text]
27. Xie ZJ, Huang YH, Askari A, et al. Studies on the specificity of the effects of oxygen metabolites on cardiac sodium pump. J Mol Cell Cardiol 1990; 22: 911–20.[Web of Science][Medline]
28. Rehberg B, Duch DS. Suppression of central nervous system sodium channels by propofol. Anesthesiology 1999; 91: 512–20.[Web of Science][Medline]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (13) Citing Articles via Google Scholar Google Scholar Articles by Daskalopoulos, R. Articles by Wilson, J. X. Search for Related Content PubMed PubMed Citation Articles by Daskalopoulos, R. Articles by Wilson, J. X. Related Collections Mechanisms Pharmacology