Mechanisms of Ca2+ handling in zebrafish ventricular myocytes
- Authors
- Bovo, E., Dvornikov, A.V., Mazurek, S.R., de Tombe, P.P., and Zima, A.V.
- ID
- ZDB-PUB-130710-130
- Date
- 2013
- Source
- Pflugers Archiv : European journal of physiology 465(12): 1775-84 (Journal)
- Registered Authors
- Keywords
- zebrafish, sarcoplasmic reticulum, sarcoplasmic reticulum, Ca2+-induced Ca2+ release, ryanodine receptor, phosphorylation, heart
- MeSH Terms
-
- Animals
- Caffeine/pharmacology
- Calcium/metabolism*
- Calcium Signaling/physiology
- Colforsin/pharmacology
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Excitation Contraction Coupling/drug effects
- Excitation Contraction Coupling/physiology*
- Myocardium/metabolism
- Myocytes, Cardiac/physiology*
- Rabbits
- Ryanodine Receptor Calcium Release Channel/physiology
- Sarcoplasmic Reticulum/metabolism*
- Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism
- Zebrafish
- PubMed
- 23821298 Full text @ Pflügers Archiv. / Eur. J. Physiol.
The zebrafish serves as a promising transgenic animal model that can be used to study cardiac Ca2+ regulation. However, mechanisms of sarcoplasmic reticulum (SR) Ca2+ handling in the zebrafish heart have not been systematically explored. We found that in zebrafish ventricular myocytes, the action potential-induced Ca2+ transient is mainly (80 %) mediated by Ca2+ influx via L-type Ca2+ channels (LTCC) and only 20 % by Ca2+ released from the SR. This small contribution of the SR to the Ca2+ transient was not the result of depleted SR Ca2+ load. We found that the ryanodine receptor (RyR) expression level in zebrafish myocytes was <72 % lower compared to rabbit myocytes. In permeabilized myocytes, increasing cytosolic [Ca2+] from 100 to 350 nM did not trigger SR Ca2+ release. However, an application of a low dose of caffeine activated Ca2+ sparks. These results show that the zebrafish cardiac RyR has low sensitivity to the mechanism of Ca2+-induced Ca2+ release. Activation of protein kinase A by forskolin increased phosphorylation of the RyR in zebrafish myocardium. In half of the studied cells, an increased Ca2+ transient by forskolin was entirely mediated by augmentation of LTCC current. In the remaining myocytes, the forskolin action was associated with an increase of both LTCC and SR Ca2+ release. These results indicate that the mechanism of excitation–contraction coupling in zebrafish myocytes differs from the mammalian one mainly because of the small contribution of SR Ca2+ release to the Ca2+ transient. This difference is due to a low sensitivity of RyRs to cytosolic [Ca2+].