The Role of Intracellular Mg2+ in Regulation of Ca2+-activated K+ Channel in Pulmonary Arterial Smooth Muscle Cells of the Rabbit

• 영문명: The Role of Intracellular Mg²⁺ in Regulation of Ca²⁺-activated K⁺ Channel in Pulmonary Arterial Smooth Muscle Cells of the Rabbit
• 발행기관: 대한생리학회-대한약리학회
• 저자명: Suk Ho Lee Myoung Kyu Park
• 간행물 정보: 『The Korean Journal of Physiology & Pharmacology』제2권 제5호, 611~616쪽, 전체 6쪽
• 주제분류: 의약학 > 의학일반
• 파일형태: PDF
• 발행일자: 1998.01.01

영문 초록

Although the Ca²⁺-activated K⁺ (I_K,Ca) channel is known to play an important role in the maintenance of resting membrane potential, the regulation of the channel in physiological condition is not completely understood in vascular myocytes. In this study, we investigated the role of cytoplasmic Mg²⁺ on the regulation of I_K,Ca channel in pulmonary arterial myocytes of the rabbit using the inside-out patch clamp technique. Mg²⁺ increased open probability (Po), but decreased the magnitude of single channel current. Mg²⁺-induced block of unitary current showed strong voltage dependence but increase of Po by Mg²⁺ was not dependent on the membrane potential. The apparent effect of Mg²⁺ might, thus, depend on the proportion between opposite effects on the Po and on the conductance of I_K,Ca channel. In low concentration of cytoplasmic Ca²⁺, Mg²⁺ increased I_K,Ca by mainly enhancement of Po. However, at very high concentration of cytoplasmic Ca²⁺, such as pCa 5.5, Mg²⁺ decreased I_K,Ca through the inhibition of unitary current. Moreover, Mg²⁺ could activate the channel even in the absence of Ca²⁺. Mg²⁺ might, therefore, partly contribute to the opening of I_K,Ca channel in resting membrane potential. This phenomenon might explain why I_K,Ca contributes to the resting membrane potential where membrane potential and concentration of free Ca²⁺ are very low.

키워드

Ca²⁺-activated K⁺ channel Mg²⁺ Pulmonary arterial smooth muscle Open probability Unitary conductance