Background:Connexin43 (Cx43) is a major connexin that forms gap junction (GJ) channels in the heart and is also present in the cell membrane as unopposed/non-junctional hemichannels and in the inner mitochondrial membrane. By using carbenoxolone (CBX), a blocker of Cx43, the effect of the blockade of Cx43 on Ca
2+waves and triggered arrhythmias in the myocardium with non-uniform contraction was examined.
Methods and Results:Trabeculae were obtained from rat hearts. Force, [Ca
2+]
i, and the diffusion coefficient were measured. Non-uniform contraction was produced with a 2,3-butanedione monoxime jet. Ca
2+waves were induced by electrical stimulation. Inducibility of arrhythmias was estimated based on the minimal [Ca
2+]
oat which arrhythmias were induced. The Ca
2+spark rate was measured in isolated single rat ventricular myocytes. CBX reduced the GJ permeability, whereas it did not change force and [Ca
2+]
itransients. CBX increased the Ca
2+leak from the sarcoplasmic reticulum in trabeculae and increased the Ca
2+spark rate in isolated single myocytes. CBX increased the velocity of Ca
2+waves and further increased the inducibility of arrhythmias. Modulation of mitochondrial K
ATPchannels by diazoxide, cromakalim and 5-hydroxydecanoic acid affected the inducibility of arrhythmias increased by CBX.
Conclusions:These results suggest that in diseased hearts, Cx43 plays an important role in the occurrence of triggered arrhythmias, probably under the modulation of mitochondrial K
ATPchannels. (
Circ J 2016;
80: 76–84)
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