The overall long-term objective of this project is to better understand the cellular mechanisms that control nter- and intracellular pH and to determine the effects of pH (extra- and intracellular) on cardiac myocyte calcium handling. The results will have considerable basic physiological importance and are highly relevant to cardiac pathophysiological conditions. Experiments will be performed on atrial and Purkinje myocytes using confocal imaging and epifluorescence techniques to measure intracellular pH, calcium and sodium (epifluorescence only) in individual cells. Flash-photolysis of caged protons will be used to generate regional ncreases in intracellular [H]. Fluorescence measurements will be coupled with current-clamp and voltage- clamp recordings of action potentials and whole cell membrane ionic currents, respectively.
The specific aims i nclude: 1. Characterize intracellular pH regulation in atrial and Purkinje cells. A detailed functional characterization of sarcolemmal pH control transporters will be performed. The results will be used to construct computational models of intracellular pH regulation. 2. Characterize electrical effects of electrogenic NBC in atrial and Purkinje cells. The relationship between NBC current and action potential repolarization and its modulation by internal pH will be determined. 3. Characterize intra- and intercellular proton diffusion in atrial and Purkinje cells. The relationship between intracellular pH and intracellular proton mobility will be determined, as well as the relationship between intracellular pH and junctional proton permeability/flux in myocyte pairs. The results will yield new insight concerning spatial control of pH in these cell types. 4. Characterize the effect of acidosis on calcium handling in atrial and Purkinje cells. The effects of whole- cell extra- and intracellular acidosis on the Ca transient, Ca current and SR Ca handling will be determined. The ability of the heart to generate electrical signals and contract is strongly influenced by the pH of the fluids inside and outside of individual cells. This research is designed to better understand the consequences of excessive accumulation of acid and base on heart cell function and to determine how the cells are able to regulate their internal pH.

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 #
5R37HL042873-24
Application #
8304967
Study Section
Special Emphasis Panel (NSS)
Program Officer
Lathrop, David A
Project Start
1989-07-01
Project End
2014-06-30
Budget Start
2012-07-01
Budget End
2014-06-30
Support Year
24
Fiscal Year
2012
Total Cost
$223,493
Indirect Cost
$74,993
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
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
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
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
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
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 Kýýý current by acidosis and its effects on excitation-contraction coupling. Am J Physiol Heart Circ Physiol 304:H1680-96
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
Ajiro, Yoichi; Saegusa, Noriko; Giles, Wayne R et al. (2011) Platelet-activating factor stimulates sodium-hydrogen exchange in ventricular myocytes. Am J Physiol Heart Circ Physiol 301:H2395-401
Saegusa, Noriko; Moorhouse, Emma; Vaughan-Jones, Richard D et al. (2011) Influence of pH on Caýýýýý current and its control of electrical and Caýýýýý signaling in ventricular myocytes. J Gen Physiol 138:537-59

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