The broad, long-term goal of this work is to establish a comprehensive understanding of the role of pH in cardiac function at the cellular level. Changes in intracellular pH (pHi) and extracellular pH have profound effects on electrical activity, excitation-contraction coupling and contraction in the heart, which accounts in part for the arrhythmias and contractile dysfunction elicited by myocardial ischemia. Compared to the information available for ventricular muscle, much less is known concerning pHi regulation, the effects of pH on Ca 2+ handling, and intra- and intercellular H+ diffusion in cardiac myocytes that lack transverse tubules (Purkinje and atrial). The protocols described in this project focus primarily on these two cell types and are designed to help fill this gap using fluorescence imaging and patch pipette techniques.
The specific aims i nclude: 1. Characterize the effect of intracellular acidosis on excitation-contraction coupling in atria/and Purkinje myocytes. The goal here is to determine the effects of acidosis on Ca 2+ current (L and T type), the spatiotemporal profile of the Ca2+ transient, Ca 2+ handling by the sarcoplasmic reticulum and intracellular Ca 2+ diffusion in these cell types. The response of [Ca2+]i to spatially confined changes in pHi will also be studied. 2. Characterize the electrogenic properties of Na-HCO3 cotransport in ventricular, atrial and Purkinje myocytes. The objective here is to test the hypothesis that Na-HCO3 cotransport is electrogenic in these cell types. 3.Characterize the properties of pH_ regulatory systems in cardiac Purkinje myocytes. The objective here is to determine the kinetic properties and pH-dependence of Na-H exchange (NHE), Na-HCO3 cotransport (NBC) and HCO3-CI exchange (AE) in isolated Purkinje myocytes and to test the hypothesis that CI-OH exchange (CHE) is operational in this cell type. 4. Characterize intra- and intercellular H+ diffusion in atrial and Purkinje cells. The goal here is to determine the intracellular H+ diffusion coefficient within single cells and the junctional permeability H+ coefficient between pairs of electrically coupled myocytes and to test the hypothesis that both parameters are modulated by carbonic anhydrase.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
5R37HL042873-18
Application #
7082884
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Program Officer
Przywara, Dennis
Project Start
1989-07-01
Project End
2008-06-30
Budget Start
2006-07-01
Budget End
2007-06-30
Support Year
18
Fiscal Year
2006
Total Cost
$172,043
Indirect Cost
Name
University of Utah
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
009095365
City
Salt Lake City
State
UT
Country
United States
Zip Code
84112
Swietach, Pawel; Spitzer, Kenneth W; Vaughan-Jones, Richard D (2015) Na? ions as spatial intracellular messengers for co-ordinating Ca²? signals during pH heterogeneity in cardiomyocytes. Cardiovasc Res 105:171-81
Lopez-Izquierdo, Angelica; Warren, Mark; Riedel, Michael et al. (2014) A near-infrared fluorescent voltage-sensitive dye allows for moderate-throughput electrophysiological analyses of human induced pluripotent stem cell-derived cardiomyocytes. Am J Physiol Heart Circ Physiol 307:H1370-7
Swietach, Pawel; Leem, Chae-Hun; Spitzer, Kenneth W et al. (2014) Pumping Ca2+ up H+ gradients: a Ca2(+)-H+ exchanger without a membrane. J Physiol 592:3179-88
Riedel, Michael; Jou, Chuanchau J; Lai, Shuping et al. (2014) Functional and pharmacological analysis of cardiomyocytes differentiated from human peripheral blood mononuclear-derived pluripotent stem cells. Stem Cell Reports 3:131-41
Torres, Natalia S; Sachse, Frank B; Izu, Leighton T et al. (2014) A modified local control model for Ca2+ transients in cardiomyocytes: junctional flux is accompanied by release from adjacent non-junctional RyRs. J Mol Cell Cardiol 68:1-11
Zhang, Xiu Q; Tang, Ruhang; Li, Ling et al. (2013) Cardiomyocyte-specific p65 NF-*B deletion protects the injured heart by preservation of calcium handling. Am J Physiol Heart Circ Physiol 305:H1089-97
Saegusa, Noriko; Garg, Vivek; Spitzer, Kenneth W (2013) Modulation of ventricular transient outward K? current by acidosis and its effects on excitation-contraction coupling. Am J Physiol Heart Circ Physiol 304:H1680-96
Venable, Paul W; Taylor, Tyson G; Sciuto, Katie J et al. (2013) Detection of mitochondrial depolarization/recovery during ischaemia--reperfusion using spectral properties of confocally recorded TMRM fluorescence. J Physiol 591:2781-94
Shibayama, Junko; Taylor, Tyson G; Venable, Paul W et al. (2013) Metabolic determinants of electrical failure in ex-vivo canine model of cardiac arrest: evidence for the protective role of inorganic pyrophosphate. PLoS One 8:e57821
Swietach, Pawel; Youm, Jae-Boum; Saegusa, Noriko et al. (2013) Coupled Ca2+/H+ transport by cytoplasmic buffers regulates local Ca2+ and H+ ion signaling. Proc Natl Acad Sci U S A 110:E2064-73

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