The long term goal of this project is to understand the regulation of cardiac muscle contraction, particularly E-C coupling and the regulation of Ca fluxes. Isolated cardiac myocytes will be used with whole cell voltage clamp and the intracellular Ca indicator, indo-1. Experiments are also planned using multicellular preparations and isolated membrane vesicles. The specific goals for the next period will be to: a) Critically evaluate intracellular calibrations of indo-1 fluorescence signals rather than rely on in vitro calibrations which are likely to be inaccurate. This will allow several important quantitative issues to be addressed (e.g. direct assessment of the pCai vs tension relation in intact cardiac muscle). b) Measure intracellular Ca buffering by measuring Ca entry, Ca extrusion and [Ca]i, providing direct information about the overall Cai required for cardiac muscle activation. c) Estimate """"""""normal"""""""" and maximal SR Ca content in different species & conditions (e.g. in """"""""Ca overload""""""""). d) Determine the fraction of SR Ca released during normal and modified contractions. e) Evaluate if Em itself can alter SR Ca release at constant SR Ca load and constant ICa """"""""trigger"""""""". f) Evaluate whether Ca entry via Na/Ca exchange can induce SR Ca release. These two studies (e & f) are important in the evaluation of postulated mechanisms of E-C coupling. g) Determine the influence of Nao on Cai transients and assess the competition between the SR and Na/Ca exchange during relaxation (and [Ca]i decline). h) Characterize Em-dependent Ca binding at the inner sarcolemmal surface which could be involved in E-C coupling since depolarization may release Ca bound to the inner sarcolemmal surface. i) Evaluate if indo-1 alters sarcolemmal Na/Ca exchange or SR Ca-ATPase complicating the use of indo-1. These studies are focused on providing important new fundamental information of a quantitative nature about the regulation of intracellular Ca and the mechanism of E-C coupling in cardiac muscle cells (e.g. force vs pCai, Cai-buffering, SR Ca content & fractional release, role of Em, Na/Ca exchange and SR in E-C coupling and relaxation). They will also provide useful new information about the use of indo-1 in cardiac muscle. Cellular Ca fluxes are in a dynamic, yet delicate balance, which will be studied in detail. The consequences of disturbing this balance can include contractile failure, spontaneous contractions (i.e. arrhythmogenic) and impair relaxation. Any of these dysfunctions will compromise the ability of the heart to function effectively as a pump. Thus, comprehensive understanding of Ca regulation in the heart is crucial.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
2R01HL030077-09A1
Application #
2216573
Study Section
Physiology Study Section (PHY)
Project Start
1982-07-01
Project End
1995-03-31
Budget Start
1991-04-01
Budget End
1992-03-31
Support Year
9
Fiscal Year
1991
Total Cost
Indirect Cost
Name
University of California Riverside
Department
Type
Schools of Medicine
DUNS #
City
Riverside
State
CA
Country
United States
Zip Code
92521
Wood, Brent M; Simon, Mitchell; Galice, Samuel et al. (2018) Cardiac CaMKII activation promotes rapid translocation to its extra-dyadic targets. J Mol Cell Cardiol 125:18-28
Hegyi, Bence; Bossuyt, Julie; Ginsburg, Kenneth S et al. (2018) Altered Repolarization Reserve in Failing Rabbit Ventricular Myocytes: Calcium and ?-Adrenergic Effects on Delayed- and Inward-Rectifier Potassium Currents. Circ Arrhythm Electrophysiol 11:e005852
Yan, Jiajie; Zhao, Weiwei; Thomson, Justin K et al. (2018) Stress Signaling JNK2 Crosstalk With CaMKII Underlies Enhanced Atrial Arrhythmogenesis. Circ Res 122:821-835
Hegyi, Bence; Bossuyt, Julie; Griffiths, Leigh G et al. (2018) Complex electrophysiological remodeling in postinfarction ischemic heart failure. Proc Natl Acad Sci U S A 115:E3036-E3044
Liu, Miao; Hoskins, Amanda; Verma, Nirmal et al. (2018) Amylin and diabetic cardiomyopathy - amylin-induced sarcolemmal Ca2+ leak is independent of diabetic remodeling of myocardium. Biochim Biophys Acta Mol Basis Dis 1864:1923-1930
Bartos, Daniel C; Morotti, Stefano; Ginsburg, Kenneth S et al. (2017) Quantitative analysis of the Ca2+ -dependent regulation of delayed rectifier K+ current IKs in rabbit ventricular myocytes. J Physiol 595:2253-2268
Sato, Daisuke; Clancy, Colleen E; Bers, Donald M (2017) Dynamics of sodium current mediated early afterdepolarizations. Heliyon 3:e00388
Surdo, Nicoletta C; Berrera, Marco; Koschinski, Andreas et al. (2017) FRET biosensor uncovers cAMP nano-domains at ?-adrenergic targets that dictate precise tuning of cardiac contractility. Nat Commun 8:15031
Lang, Di; Sato, Daisuke; Jiang, Yanyan et al. (2017) Calcium-Dependent Arrhythmogenic Foci Created by Weakly Coupled Myocytes in the Failing Heart. Circ Res 121:1379-1391
De Jesus, Nicole M; Wang, Lianguo; Lai, Johnny et al. (2017) Antiarrhythmic effects of interleukin 1 inhibition after myocardial infarction. Heart Rhythm 14:727-736

Showing the most recent 10 out of 80 publications