Critical role of bicarbonate and bicarbonate transporters in cardiac function

• 作者: Gary E Shull Hong-Sheng Wang Kanimozhi Vairamani Yamei Chen
• 来源期刊: 世界生物化学杂志：英文版（电子版）
• 学科: 生物学
• 关键词: SLC4 SLC26 Slc26a6 AE1 AE2 NBCn1
• 年，卷（期）: 2014,（3）
• 页码范围: 334-345
• 页数: 12页
• 分类号: Q463

摘要

Bicarbonate is one of the major anions in mammalian tissues and extracellular fluids. Along with accompanying H+, HCO3- is generated from CO2 and H2 O, either spontaneously or via the catalytic activity of carbonic anhydrase. It serves as a component of the major buffer system, thereby playing a critical role in pH homeostasis. Bicarbonate can also be utilized by a variety of ion transporters, often working in coupled systems, to transport other ions and organic substrates across cell membranes. The functions of HCO3- and HCO3--transporters in epithelial tissues have been studied extensively, but their functions in heart are less well understood. Here we review studies of the identities and physiological functions of Cl-/HCO3- exchangers and Na+/HCO3-cotransporters of the SLC4 A and SLC26 A families in heart. We also present RNA Seq analysis of their cardiac mRNA expression levels. These studies indicate that slc4a3(AE3) is the major Cl-/HCO3- exchanger and plays a protective role in heart failure, and that Slc4a4(NBCe1) is the major Na+/HCO3- cotransporter and affects action potential duration. In addition, previous studies show that HCO3- has a positive inotropic effect in the perfused heart that is largely independent of effects on intracellular Ca2+. The importance of HCO3- in the regulation of contractility is supported by experiments showing that isolated cardiomyocytes exhibit sharply enhanced contractility, with no change in Ca2+ transients, when switched from Hepes-buffered to HCO3-- buffered solutions. These studies demonstrate that HCO3- and HCO3--handling proteins play important roles in the regulation of cardiac function.