title: Cytoplasmic pH change induced by leukotriene B4 in human neutrophils.
abstract: Leukotriene B4 induced a biphasic change in the cytoplasmic pH of human neutrophils: an initial rapid acidification followed by an alkalinization. The acidification was slightly reduced by the removal of extracellular Ca2+, but the subsequent alkalinization was not. The leukotriene B4-induced alkalinization was dependent on extracellular Na+ and pH, and was inhibited by amiloride and its more potent analogue, 5-(N,N-hexamethylene)amiloride. These characteristics indicate that the cytoplasmic alkalinization is mediated by the Na+-H+ exchange. Oxidation products of leukotriene B4, 20-hydroxyleukotriene B4, 20-carboxyleukotriene B4, and (5S)-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) also stimulated the Na+-H+ exchange, but higher concentrations were required. Treatment of the cells with pertussis toxin inhibited both phases of the leukotriene B4-induced pHi change, while cholera toxin did not affect the pHi change. The alkalinization induced by leukotriene B4 was inhibited by 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), an inhibitor of protein kinase C, but was not inhibited by N-(2-guanidinoethyl)-5-isoquinolinesulfonamide which has a less inhibitory effect on protein kinase C. Acidification was not affected by the drugs. These findings suggest that a GTP-binding protein sensitive to pertussis toxin and protein kinase C are involved in the activation of the Na+-H+ exchange stimulated by leukotriene B4.
authors.affiliation: Department of Biochemistry, Kyushu University School of Medicine, Fukuoka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sumimoto
authors.forename: M
authors.initials: M
authors.lastname: Satoh
authors.forename: K
authors.initials: K
authors.lastname: Takeshige
authors.forename: E J
authors.initials: EJ
authors.lastname: Cragoe
authors.forename: S
authors.initials: S
authors.lastname: Minakami
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000081:Acetamides / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002634:Chemotaxis, Leukocyte; D003593:Cytoplasm / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology; D007975:Leukotriene B4 / Q000494:pharmacology*; D009504:Neutrophils / Q000502:physiology*; D037342:Pertussis Toxin; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D017923:Sodium-Hydrogen Exchangers; D013997:Time Factors; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D000081:Acetamides; D002352:Carrier Proteins; D007546:Isoquinolines; D010879:Piperazines; D017923:Sodium-Hydrogen Exchangers; D010566:Virulence Factors, Bordetella; D007975:Leukotriene B4; D000584:Amiloride; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; C014026:hexamethylene bisacetamide