title: Functional characterization of intracellular pH regulators responsible for acid extrusion in human radial artery smooth muscle cells.
abstract: Intracellular pH (pHi) is a critical factor influencing many important cellular functions. Acid extrusion carriers such as an Na⁺/H⁺ exchanger (NHE) Na⁺/HCO₃⁻ cotransporter (NBC) and monocarboxylate transporters (MCT) can be activated when cells are in an acidic condition (pHi < 7.1). Human radial artery smooth muscle cells (HRASMC) is an important conduit in coronary artery bypass graft surgery. However, such far, the pHi regulators have not been characterized in HRASMCs. We therefore investigated the mechanism of pHi recovery from intracellular acidosis and alkalosis, induced by NH₄Cl-prepulse and Na-acetate-prepulse, respectively, using intracellular 2',7'-bis(2-carboxethyl)-5(6)- carboxy-fluorescein (BCECF)-fluorescence in HRASMCs. Cultured HRASMCs were derived from the segments of human radial artery that were obtained from patients undergoing bypass grafting. The resting pHi is 7.22 ± 0.03 and 7.17 ± 0.02 for HEPES- (nominally HCO₃⁻-free) and CO₂/HCO₃⁻- buffered solution, respectively. In HEPES-buffered solution, a pHi recovery from induced intracellular acidosis could be blocked completely by 30 μM HOE 694 (3-methylsulfonyl-4-piperidinobenzoyl, guanidine hydrochloride) a specific NHE inhibitor, or by removing [Na⁺]₀. In 3% CO₂/HCO₃⁻-buffered solution, HOE 694 slowed the pHi recovery from the induced intracellular acidosis only, while adding together with DIDS (a specific NBC inhibitor) or removal of [Na⁺]₀ entirely inhibited the acid extrusion. Moreover, α-cyano-4-hydroxycinnamate (CHC; a specific blocker of MCT) blocked the lactate-induced pHi changes. In conclusion, we demonstrate, for the first time, that 3 different pHi regulators responsible for acid extruding, i.e. NHE and NBC, and MCT, are functionally co-existed in cultured HRASMCs.
authors.affiliation: Department of Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490 Taiwan, Republic of China.
authors.forename: Chung-Yi
authors.initials: CY
authors.lastname: Lee
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Tsai
authors.forename: Chung-Yi
authors.initials: CY
authors.lastname: Chang
authors.forename: Yi-Yu
authors.initials: YY
authors.lastname: Chang
authors.forename: Tzu-Hurng
authors.initials: TH
authors.lastname: Cheng
authors.forename: Chien-Sung
authors.initials: CS
authors.lastname: Tsai
authors.forename: Shih-Hurng
authors.initials: SH
authors.lastname: Loh
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000136:Acid-Base Equilibrium / Q000187:drug effects / Q000502:physiology*; D000138:Acidosis / Q000378:metabolism; D000143:Acids / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003373:Coumaric Acids / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D027501:Monocarboxylic Acid Transporters / Q000009:adverse effects / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D061251:Primary Cell Culture; D017534:Radial Artery / Q000166:cytology; D027982:Sodium-Bicarbonate Symporters / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013450:Sulfones / Q000494:pharmacology; D027981:Symporters / Q000009:adverse effects / Q000378:metabolism*; D000099233:Monocarboxylate Transport Protein 1
chemical_list: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D000143:Acids; D027682:Cation Transport Proteins; D003373:Coumaric Acids; D006146:Guanidines; D027501:Monocarboxylic Acid Transporters; D027982:Sodium-Bicarbonate Symporters; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; D027981:Symporters; D000099233:Monocarboxylate Transport Protein 1; C422022:SLC4A7 protein, human; C490998:SLC9A1 protein, human; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine