Decreased inward rectifier and voltage-gated K+ currents of the right septal coronary artery smooth muscle cells in pulmonary arterial hypertensive rats
Sung Eun Kim1,2,#, Ming Zhe Yin1,2,#, Hae Jin Kim1,2, Rany Vorn3, Hae Young Yoo3,*, and Sung Joon Kim1,2,4,*
Departments of 1Physiology and 2Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, 3Department of Nursing, Chung-Ang University, Seoul 06974, 4Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 03080, Korea
Received: October 10, 2019; Revised: November 28, 2019; Accepted: November 28, 2019
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
In vascular smooth muscle, K+ channels, such as voltage-gated K+ channels (Kv), inward-rectifier K+ channels (Kir), and big-conductance Ca2+-activated K+ channels (BKCa), establish a hyperpolarized membrane potential and counterbalance the depolarizing vasoactive stimuli. Additionally, Kir mediates endothelium-dependent hyperpolarization and the active hyperemia response in various vessels, including the coronary artery. Pulmonary arterial hypertension (PAH) induces right ventricular hypertrophy (RVH), thereby elevating the risk of ischemia and right heart failure. Here, using the whole-cell patch-clamp technique, we compared Kv and Kir current densities (IKv and IKir) in the left (LCSMCs), right (RCSMCs), and septal branches of coronary smooth muscle cells (SCSMCs) from control and monocrotaline (MCT)-induced PAH rats exhibiting RVH. In control rats, (1) IKv was larger in RCSMCs than that in SCSMCs and LCSMCs, (2) IKv inactivation occurred at more negative voltages in SCSMCs than those in RCSMCs and LCSMCs, (3) IKir was smaller in SCSMCs than that in RCSMCs and LCSMCs, and (4) IBKCa did not differ between branches. Moreover, in PAH rats, IKir and IKv decreased in SCSMCs, but not in RCSMCs or LCSMCs, and IBKCa did not change in any of the branches. These results demonstrated that SCSMC-specific decreases in IKv and IKir occur in an MCT-induced PAH model, thereby offering insights into the potential pathophysiological implications of coronary blood flow regulation in right heart disease. Furthermore, the relatively smaller IKir in SCSMCs suggested a less effective vasodilatory response in the septal region to the moderate increase in extracellular K+ concentration under increased activity of the myocardium.