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Heterogeneous Kv1 function and expression in coronary myocytes from right and left ventricles in rats

Laboratoire de Physiopathologie de la Paroi Artérielle, Université François Rabelais, Tours, France

Submitted 21 July 2005 ; accepted in final form 19 May 2006

Coronary blood flow control is not uniform along the vascular tree and particularly between the right coronary artery and the left anterior descending artery. Resting membrane potential that contributes largely to the vascular tone is mainly regulated by K⁺ channels in coronary myocytes. In the present study, we hypothesized that right coronary artery (RCA) and left coronary artery (LCA) exhibited a cell-specific function of K⁺ channels. The net outward current was markedly greater in RCA compared with LCA cells, and this difference was due to a larger 4-aminopyridine (4-AP)-sensitive voltage-gated potssium (Kv) current in RCA cells, whereas the iberiotoxin (IbTx)-sensitive, large conductance Ca²⁺-dependent potassium (BK_Ca) current was smaller in RCA cells. To go further in the molecular identity of this Kv current, we used 50 nM correolide, which specifically blocked Kv1 family -subunits. Outward currents generated by ramp depolarization protocols were highly sensitive to correolide in both RCA and LCA cells, suggesting that Kv1 contributed for a large part to the net outward current. 4-AP-induced contractions in isolated RCA, and LCA were greater than IbTx-induced contraction. Furthermore, the 4-AP-induced contraction in RCA was significantly greater than that in LCA, which is in agreement with the electrophysiological data. Finally, the Kv1.2 -subunit but not the Kv1.5 was detected in both RCA and LCA using primary specific antibody in Western blotting and immunofluorescence assay, and expression of Kv1.2 -subunit was markedly higher in RCA compared with LCA. In summary, we reported for the first time a heterogeneous function and expression of Kv1 -subunits in rat coronary myocytes isolated from RCA or LCA.

coronary circulation; potassium channel; perfused coronary; membrane currents