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(Circulation Research. 2003;93:541.)
© 2003 American Heart Association, Inc.

Cellular Biology

Changes in the Ca²⁺-Activated K⁺ Channels of the Coronary Artery During Left Ventricular Hypertrophy

Nari Kim, Joonyong Chung, Euiyong Kim, Jin Han

From the Departments of Physiology & Biophysics (N.K., E.K., J.H.) and Parasitology (J.C.), College of Medicine, Inje University, Busan, Korea.

Correspondence to Jin Han, MD, PhD, Department of Physiology & Biophysics, College of Medicine, Inje University, 633-165 Gaegeum-Dong, Busanjin-Gu, Busan 613-735, Korea. E-mail phyhanj{at}ijnc.inje.ac.kr

It has been suggested that impairment of smooth muscle cell (SMC) function by alterations in the Ca²⁺-activated K⁺ (K_Ca) channels accounts for the reduction in coronary reserve during left ventricular hypertrophy (LVH). However, this hypothesis has not been fully investigated. The main goal of this study was to assess whether the properties of K_Ca channels in coronary SMCs were altered during LVH. In patch-clamp experiments, the whole-cell currents of the K_Ca channels were reduced during LVH. The unitary current amplitude and open probability for the K_Ca channels were significantly reduced in LVH patches compared with control patches. The concentration-response curve of the K_Ca channel to [Ca²⁺]_i was shifted to the right. Inhibition of the K_Ca channels by tetraethylammonium (TEA) was more pronounced in LVH cells than in control cells. Western blot analysis indicated no differences in K_Ca channel expression between the control and LVH coronary SM membranes. In contraction experiments, the effect of high K⁺ concentration on the resting tension of the LVH coronary artery was greater than on that of the control. The effect of TEA on the resting tension of the LVH coronary artery was reduced compared with the effect on the control. Our findings imply a novel mechanism for reduced coronary reserve during LVH.

Key Words: left ventricular hypertrophy • reduced coronary reserve • K_Ca channels • smooth muscle cells

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