Article

Sarcoplasmic reticulum Ca2+ release is not a dominating factor in sinoatrial node pacemaker activity.

Department of Humoral Regulation, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
Circulation Research (impact factor: 9.49). 03/2003; 92(3):e41-4. pp.e41-4
Source: PubMed

ABSTRACT Recent work on isolated sinoatrial node cells from rabbit has suggested that sarcoplasmic reticulum Ca2+ release plays a dominant role in the pacemaker potential, and ryanodine at a high concentration (30 micromol/L blocks sarcoplasmic reticulum Ca2+ release) abolishes pacemaking and at a lower concentration abolishes the chronotropic effect of beta-adrenergic stimulation. The aim of the present study was to test this hypothesis in the intact sinoatrial node of the rabbit. Spontaneous activity and the pattern of activation were recorded using a grid of 120 pairs of extracellular electrodes. Ryanodine 30 micromol/L did not abolish spontaneous activity or shift the position of the leading pacemaker site, although it slowed the spontaneous rate by 18.9+/-2.5% (n=6). After ryanodine treatment, beta-adrenergic stimulation still resulted in a substantial chronotropic effect (0.3 micromol/L isoproterenol increased spontaneous rate by 52.6+/-10.5%, n=5). In isolated sinoatrial node cells from rabbit, 30 micromol/L ryanodine slowed spontaneous rate by 21.5+/-2.6% (n=13). It is concluded that sarcoplasmic reticulum Ca2+ release does not play a dominating role in pacemaking in the sinoatrial node. The full text of this article is available at http://www.circresaha.org.

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Keywords

30 micromol/L blocks sarcoplasmic reticulum Ca2+ release
 
30 micromol/L ryanodine
 
beta-adrenergic stimulation
 
chronotropic effect
 
dominant role
 
dominating role
 
extracellular electrodes
 
full text
 
intact sinoatrial node
 
leading pacemaker site
 
lower concentration abolishes
 
Recent work
 
Ryanodine 30 micromol/L
 
ryanodine treatment
 
sarcoplasmic reticulum Ca2+ release
 
sinoatrial node
 
sinoatrial node cells
 
Spontaneous activity
 
spontaneous rate
 
substantial chronotropic effect
 

H Honjo