title: Role of Na(+)/H(+) exchanger during O(2) deprivation in mouse CA1 neurons.
abstract: To determine the role of membrane transporters in intracellular pH (pH(i)) regulation under conditions of low microenvironmental O(2), we monitored pH(i) in isolated single CA1 neurons using the fluorescent indicator carboxyseminaphthorhodafluor-1 and confocal microscopy. After total O(2) deprivation or anoxia (PO(2) approximately equal to 0 Torr), a large increase in pH(i) was seen in CA1 neurons in HEPES buffer, but a drop in pH(i), albeit small, was observed in the presence of HCO(3)(-). Ionic substitution and pharmacological experiments showed that the large anoxia-induced pH(i) increase in HEPES buffer was totally Na(+) dependent and was blocked by HOE-694, strongly suggesting the activation of the Na(+)/H(+) exchanger (NHE). Also, this pH(i) increase in HEPES buffer was significantly smaller in Na(+)/H(+) exchanger isoform 1 (NHE1) null mutant CA1 neurons than in wild-type neurons, demonstrating that NHE1 is responsible for part of the pH(i) increase following anoxia. Both chelerythrine and H-89 partly blocked, and H-7 totally eliminated, this anoxia-induced pH(i) increase in the absence of HCO. We conclude that 1) O(2) deprivation activates Na(+)/H(+) exchange by enhancing protein kinase activity and 2) membrane proteins, such as NHE, actively participate in regulating pH(i) during low-O(2) states in neurons.
authors.affiliation: Section of Respiratory Medicine, Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
authors.forename: H
authors.initials: H
authors.lastname: Yao
authors.forename: X Q
authors.initials: XQ
authors.lastname: Gu
authors.forename: R M
authors.initials: RM
authors.lastname: Douglas
authors.forename: G G
authors.initials: GG
authors.lastname: Haddad
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000143:Acids / Q000378:metabolism; D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D015687:Cell Hypoxia / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006146:Guanidines / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology*; D006863:Hydrogen-Ion Concentration; D002534:Hypoxia, Brain / Q000378:metabolism*; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D051379:Mice; D008818:Mice, Neurologic Mutants; D009474:Neurons / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology*; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013449:Sulfonamides; D013450:Sulfones / Q000494:pharmacology
chemical_list: D000143:Acids; D000470:Alkaloids; D053119:Benzophenanthridines; D004791:Enzyme Inhibitors; D006146:Guanidines; D007546:Isoquinolines; D010617:Phenanthridines; D017923:Sodium-Hydrogen Exchangers; D013449:Sulfonamides; D013450:Sulfones; C069139:growth factor-activatable Na-H exchanger NHE-1; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D012964:Sodium; C016299:chelerythrine; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D010100:Oxygen