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: Chung-Yi Lee, Yi-Ting Tsai, Chung-Yi Chang, Yi-Yu Chang, Tzu-Hurng Cheng, Chien-Sung Tsai, Shih-Hurng Loh
• Journal: The Chinese journal of physiology (Chin J Physiol) Vol. 57 Issue 5 Pg. 238-48 (Oct 31 2014) ISSN: 0304-4920 [Print] India
• PMID: 25241983 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Acids
• Cation Transport Proteins
• Coumaric Acids
• Guanidines
• Monocarboxylic Acid Transporters
• SLC4A7 protein, human
• SLC9A1 protein, human
• Sodium-Bicarbonate Symporters
• Sodium-Hydrogen Exchanger 1
• Sodium-Hydrogen Exchangers
• Sulfones
• Symporters
• monocarboxylate transport protein 1
• 3-methylsulfonyl-4-piperidinobenzoyl guanidine
• 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid

Topics

• 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid (pharmacology)
• Acid-Base Equilibrium (drug effects, physiology)
• Acidosis (metabolism)
• Acids (metabolism)
• Cation Transport Proteins (antagonists & inhibitors, metabolism)
• Coumaric Acids (pharmacology)
• Guanidines (pharmacology)
• Humans
• Hydrogen-Ion Concentration
• Models, Biological
• Monocarboxylic Acid Transporters (adverse effects, metabolism)
• Muscle, Smooth, Vascular (cytology)
• Myocytes, Smooth Muscle (cytology, drug effects, metabolism)
• Primary Cell Culture
• Radial Artery (cytology)
• Sodium-Bicarbonate Symporters (antagonists & inhibitors, metabolism)
• Sodium-Hydrogen Exchanger 1
• Sodium-Hydrogen Exchangers (antagonists & inhibitors, metabolism)
• Sulfones (pharmacology)
• Symporters (adverse effects, metabolism)