Abstract
BACKGROUND: Focal “discharges” from the Purkinje network were shown to trigger VTs and VFs in ischemic hearts. In dog model of myocardial infarction, this Purkinje ectopy was attributed to abnormal oscillations of Ca 2+ concentration in Purkinje cells (Pcells). The cause of these oscillations is unknown mostly because important features of Ca 2+ handling of normal Pcells remain obscure. It was proposed that distinct forms of Ca 2+ channels participate to Ca 2+ release from endoplasmic reticulum (ER) in canine Pcells, wherein RyR3 was found to co-exist with IP3R and RyR2. Nevertheless, presence of this system of multiple Ca 2+ channels has not been explored in other species and the function of this system in Pcells remains unclear. Here, we examined the hypothesis that a specific region of RyR3 Ca 2+ release exists in Pcells of large size hearts and forms anatomical and functional coupling between membrane and core ER-Ca 2+ releases. METHODS: Purkinje strands were dissected from hearts of 36 Yucatan swine. Enzymatically dispersed Pcells were loaded with Fluo4. Intracellular Ca 2+ dynamics was assessed by 2D confocal imaging (92cells). Function of ER-Ca 2+ channels was investigated through effects of selective inhibitors on intracellular Ca 2+ transients (65cells). mRNA level was measured in Purkinje fibers by RT-PCR for RyR isoforms 1,2,3 and IP3R (11 animals). Protein expression was characterized by immunofluorescence (34 cells). RESULTS: Compared to myocardium, 100fold larger RyR3 mRNA level was detected in Purkinje fibers. 3D distribution of RyR3-Ab revealed a concentric RyR3 layer at the cell periphery. Spark rate-pCarelations showed that Ca 2+ sensitivity of ER-Ca 2+ release at the Pcell periphery was 2fold larger than further in the core. 3 distinct velocities were detected in the typical centripetal Ca 2+ propagation of Pcells. RyR3 inhibitor dantrolene (10µM) immediately reduced the Ca 2+ release event rate by 50% in the periphery only. CONCLUSION: RyR3 is a major component of the specific Ca 2+ signaling of Pcells of large mammalian heart, suggesting that any RyR3 alteration may cause pro-arrhythmic Ca 2+ abnormalities in ischemic heart. Purkinje-specificity of RyR3 highlights a new target for selective treatment of Purkinje-originated dysrhythmia.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
