Functional Characterization of Intracellular pH Regulators Responsible for Acid Extrusion in Human Radial Artery Smooth Muscle Cells

Chung-Yi Lee ； Yi-Ting Tsai ； Chung-Yi Chang ； Yi-Yu Chang ； Tzu-Hurng Cheng ； Chien-Sung Tsai ； Shih-Hurng Loh

《The Chinese Journal of Physiology》 57卷5期 (2014/10) Pp. 238-248

https://doi.org/10.4077/CJP.2014.BAD269

並列摘要

Intracellular pH (pH_i) is a critical factor influencing many important cellular functions. Acid extrusion carriers such as Na^+/H^+ exchanger (NHE), Na^+/HCO_3^- cotransporter (NBC) and monocarboxylate transporters (MCT) can be activated when cells are in an acidic condition (pH_i＜7.1). Human radial artery smooth muscle cells (HRASMCs) are an important conduit in coronary artery bypass graft surgery. However, such far, the pH_i regulators have not been characterized in HRASMCs. We therefore investigated the mechanism of pH_i recovery from intracellular acidosis and alkalosis, induced by NH_4Cl-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 pH_i is 7.22±0.03 and 7.17±0.02 for HEPES-(nominally HCO_3^--free) and CO_2/HCO_3^--buffered solution, respectively. In HEPES-buffered solution, a pH_i 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^+]o. In 3% CO_2/HCO_3^--buffered solution, HOE 694 slowed the pH_i recovery from the induced intracellular acidosis only, while adding together with DIDS (a specific NBC inhibitor) or removal of [Na^+]o entirely inhibited the acid extrusion. Moreover, α-cyano-4-hydroxycinnamate (CHC; a specific blocker of MCT) blocked the lactate-induced pH_i changes. In conclusion, we demonstrate, for the first time, those 3 different pH_i regulators responsible for acid extruding, i.e. NHE and NBC, and MCT, are functionally co-existed in cultured HRASMCs.

並列關鍵字

BCECF ； human radial artery smooth muscle cells (HRASMCs) ； intracellular pH (pH_i) ； monocarboxylate transporters (MCT) ； Na^+-H^+ exchanger (NHE) ； Na^+-HCO_3^- cotransporter (NBC)

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