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The mouse sino-atrial node expresses both the type 2 and type 3 Ca(2+) release channels/ryanodine receptors
Haruko Masumiya1, Hideyuki Yamamoto, Myriam Hemberger
1Department of Bio-informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Japan. h-masumiya.bip@mri.tmd.ac.jp
Abstract:
Ca(2+) released from intracellular Ca(2+) stores is shown to be involved in pacemaker activity in the sino-atrial (SA)-node. However, little is known about the molecular identity of the Ca(2+) release channel/ryanodine receptor (RYR) involved in pacemaker activity. We examined the mRNA distribution of three different RYR isoforms (RYR1, RYR2, and RYR3) in the mouse SA-node. RNase protection assay and in situ hybridization revealed that RYR2 mRNA expresses widely in the heart including the SA-node, while RYR3 mRNA expression is limited to the SA-node and to the right atrium. Thus, not only RYR2 but also RYR3 may participate in pacemaker activity.