The applicants' broad and long term objectives are to investigate excitation contraction (EC) coupling and in' particular mechanisms by which sarcoplasmic reticular (SR) Ca release is triggered in mammalian heart. Defects in the mechanism of EC coupling may be central to such health related problems as the long QT syndrome, heart failure and various cardiomypathies.
The specific aims mainly involve establishing that the relationship between trigger Ca and SR Ca release is non linear so that two separate triggers e.g. T type Ca current or Na-Ca exchange sum their effects with L type Ca current in a non linear fashion. Thus small triggers might have effects that are disproportionately large. Therefore the influence of small triggers could be significant in regulating SR Ca release.
The specific aims are 1) To investigate the relationships between SR Ca release triggers and SR Ca release 2) To investigate the relationship between Ca sparks and SR release triggers and 3) To investigate the effect of Na current on both macroscopic and microscopic gain.
These specific aims will be approached with the following basic research design and methods. The relationship between SR Ca release and Ca current will be measured at constant voltage using voltage clamp, fluorescent indicators (Fluo-3) and a rapid solution-changing device. The relationship between SR Ca release and Ca current will be established at several different but constant voltages. For example the relationship will be established at -10 mV and at +50 mV. From these relationships the macroscopic gain of the system will be calculated as the rate of SR Ca release divided by the magnitude of the L type Ca current. The effect of intracellular Na, Na current and reverse Na-Ca exchange on this relationship will be established. Ca sparks will be measured with a confocal microscope operating in line scan mode in both Rabbit and Mouse ventricular myocytes at 36 degrees C using the Ca indicator Fluo-3. The hypothesis that the probability of spark occurrence that is activated by Ca current can be influenced by Na-Ca exchange will be measured by comparing spark occurrence in transgenic mice overexpressing the Na-Ca exchange and wildtype mice which do not. The design of these experiments is such that sparks can be measured in a fixed location in one confocal plane thus greatly simplifying the analysis. Finally the effect of Na, Na-Ca exchange and controlled Na currents on microscopic gain will be tested.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL062690-02
Application #
6184878
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Project Start
1999-05-01
Project End
2003-04-30
Budget Start
2000-05-01
Budget End
2001-04-30
Support Year
2
Fiscal Year
2000
Total Cost
$282,977
Indirect Cost
Name
University of Utah
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
City
Salt Lake City
State
UT
Country
United States
Zip Code
84112
Zahradníková, Alexandra; Gaburjáková, Marta; Bridge, John H B et al. (2010) Challenging quantal calcium signaling in cardiac myocytes. J Gen Physiol 136:581-3
Larbig, Robert; Torres, Natalia; Bridge, John H B et al. (2010) Activation of reverse Na+-Ca2+ exchange by the Na+ current augments the cardiac Ca2+ transient: evidence from NCX knockout mice. J Physiol 588:3267-76
Torres, Natalia S; Larbig, Robert; Rock, Alex et al. (2010) Na+ currents are required for efficient excitation-contraction coupling in rabbit ventricular myocytes: a possible contribution of neuronal Na+ channels. J Physiol 588:4249-60
Sachse, Frank B; Savio-Galimberti, Eleonora; Goldhaber, Joshua I et al. (2009) Towards computational modeling of excitation-contraction coupling in cardiac myocytes: reconstruction of structures and proteins from confocal imaging. Pac Symp Biocomput :328-39
Sobie, Eric A; Cannell, Mark B; Bridge, John H B (2008) Allosteric activation of Na+-Ca2+ exchange by L-type Ca2+ current augments the trigger flux for SR Ca2+ release in ventricular myocytes. Biophys J 94:L54-6
Savio-Galimberti, Eleonora; Frank, Joy; Inoue, Masashi et al. (2008) Novel features of the rabbit transverse tubular system revealed by quantitative analysis of three-dimensional reconstructions from confocal images. Biophys J 95:2053-62
Bridge, John H B; Savio-Galimberti, Eleonora (2008) What are the consequences of phosphorylation and hyperphosphorylation of ryanodine receptors in normal and failing heart? Circ Res 102:995-7
Sachse, Frank B; Savio-Galimberti, Eleonora; Goldhaber, Joshua I et al. (2008) Sub-micrometer anatomical models of the sarcolemma of cardiac myocytes based on confocal imaging. Pac Symp Biocomput :390-401
Bridge, John H B; Davidson, Christopher J; Savio-Galimberti, Eleonora (2006) A novel mechanism of pacemaker control that depends on high levels of cAMP and PKA-dependent phosphorylation: a precisely controlled biological clock. Circ Res 98:437-9
Inoue, Masashi; Bridge, John H B (2005) Variability in couplon size in rabbit ventricular myocytes. Biophys J 89:3102-10

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