抄録
[Aim] Pulmonary veins (PVs) are major arrhythmogenic foci to initiate and perpetuate atrial fibrillation. Previous electrophysiological studies demonstrated myocardial cells in PVs next to the left atrium (myocardial sleeve) show spontaneous pacemaker activities, but its molecular basis is still unclear. We investigated mRNA and protein level of the PV in comparison with the SA node (SAN) and the right atrium (RA). [Methods] Tissue samples from PV, SAN and RA were dissected from rabbit hearts (n=7). Quantative real-time PCR was used to quantify mRNA expression for connexin (Cx)45, Cx43, Cx40, hyperpolarization-activated nucleotide-gated channels (HCN1, 4), L-type calcium channel alpha-subunits (Cav1.2, 1.3), cardiac-type sodium channel alpha-subunit (Nav1.5), atrial natreutic peptide (ANP) and middle neurofilament (NF-M). Protein expression of HCN1,4 and Cxs was estimated by immunohistochemistry. [Results] In comparison with RA, SAN was characterized by higher mRNA levels of Cx 45, HCN1, HCN4, Cav1.3 and NF-M and a lower mRNA levels of Cx43, Cx40, Cav1.2, Nav1.5 and ANP. PV, like SAN, had a lower mRNAs of ANP and Nav1.5, but mRNAs of Cx43, Cx45, Cx40, HCN1, HCN4, Cav1.2, Cav1.3 and NF-M were comparable to RA. Unlike SAN, proteins of Cx45, HCN1 and HCN4 were not recognized in PV. [Conclusions] The PV exhibited different mRNA and protein expression profiles than SAN in terms of ion channels and connexins. The spontaneous pacemaker activity of PV cannot be attributed to HCN1,4 and Cav1.3 channels. [Jpn J Physiol 55 Suppl:S87 (2005)]
