Epac-induced ryanodine receptor type 2 activation inhibits sodium currents in atrial and ventricular murine cardiomyocytes.
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Authors
Valli, Haseeb
Ahmad, Shiraz
Sriharan, Sujan
Dean, Lydia D
Grace, Andrew
Matthews, Hugh
Publication Date
2018-03Journal Title
Clinical and experimental pharmacology & physiology
ISSN
0305-1870
Publisher
Wiley-Blackwell
Volume
45
Issue
3
Pages
278-292
Language
eng
Type
Article
This Version
VoR
Physical Medium
Print-Electronic
Metadata
Show full item recordCitation
Valli, H., Ahmad, S., Sriharan, S., Dean, L. D., Grace, A., Jeevaratnam, K., Matthews, H., & et al. (2018). Epac-induced ryanodine receptor type 2 activation inhibits sodium currents in atrial and ventricular murine cardiomyocytes.. Clinical and experimental pharmacology & physiology, 45 (3), 278-292. https://doi.org/10.1111/1440-1681.12870
Abstract
Acute RyR2 activation by exchange protein directly activated by cAMP (Epac) reversibly
perturbs myocyte Ca2+ homeostasis, slows myocardial action potential conduction, and exerts
pro-arrhythmic effects. Loose patch-clamp studies, preserving in vivo extracellular and
intracellular conditions, investigated Na+ current in intact cardiomyocytes in murine atrial
and ventricular preparations following Epac activation. Depolarising steps to varying test
voltages activated typical voltage-dependent Na+ currents. Plots of peak current against
depolarisation from resting potential gave pretreatment maximum atrial and ventricular
currents of -20.23±1.48(17) and -29.8±2.4(10) pA/μm2 (means± SEM (n)). Challenge by 8-
CPT (1 μM) reduced these currents to -11.21±0.91(12) (p<0.004) and -19.3±1.6(11) pA/μm2
(p<0.04) respectively. Currents following further addition of the RyR2 inhibitor dantrolene
(10 μM) (-19.91±2.84(13) and -26.6±1.7(17)), and dantrolene whether alone (-19.53±1.97(8)
and -27.6±1.9(14)) or combined with 8-CPT (-19.93±2.59(12) and -29.9±2.5(11)), were
indistinguishable from pretreatment values (all p>>0.05). Assessment of the inactivation that
followed by applying subsequent steps to a fixed voltage 100 mV positive to resting potential
gave concordant results. Half-maximal inactivation voltages and steepness factors, and time
constants for Na+ current recovery from inactivation in double-pulse experiments, were
similar through all the pharmacological conditions. Intracellular sharp microelectrode
membrane potential recordings in intact Langendorff-perfused preparations demonstrated
concordant variations in maximum rates of atrial and ventricular action potential upstroke,
(dV/dt)max. We thus demonstrate an acute, reversible, Na+ channel inhibition offering a
possible mechanism for previously reported pro-arrhythmic slowing of AP propagation
following modifications of Ca2+ homeostasis, complementing earlier findings from chronic
alterations in Ca2+ homeostasis in genetically modified RyR2-P2328S hearts.
Keywords
Heart, Myocytes, Cardiac, Animals, Mice, Inbred C57BL, Mice, Calcium, Dantrolene, Guanine Nucleotide Exchange Factors, Ryanodine Receptor Calcium Release Channel, Sodium Channels, Cyclic AMP, Muscle Relaxants, Central, Patch-Clamp Techniques, Microelectrodes, Gene Expression Regulation, Action Potentials
Sponsorship
British Heart Foundation (PG/14/79/31102)
WELLCOME TRUST (105727/Z/14/Z)
MRC (MR/M001288/1)
British Heart Foundation (PG/15/12/31280)
Identifiers
External DOI: https://doi.org/10.1111/1440-1681.12870
This record's URL: https://www.repository.cam.ac.uk/handle/1810/276107
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