title: Mg(2+)-dependent facilitation and inactivation of L-type Ca(2+) channels in guinea pig ventricular myocytes.
abstract: This study aimed to investigate the intracellular Mg(2+) regulation of the L-type Ca(2+) channels in guinea pig ventricular myocytes. By adopting the inside-out configuration of the patch clamp technique, single channel currents of the L-type Ca(2+) channels were recorded at different intracellular Mg(2+) concentrations ([Mg(2+)]i). At free [Mg(2+)]i of 0, 10(-9), 10(-7), 10(-5), 10(-3), and 10(-1) M, 1.4 μM CaM + 3 mM ATP induced channel activities of 44%, 117%, 202%, 181%, 147%, and 20% of the control activity in cell-attached mode, respectively, showing a bell-shaped concentration-response relationship. Moreover, the intracellular Mg(2+) modulated the Ca(2+) channel gating properties, accounting for alterations in channel activities. These results imply that Mg(2+) has a dual effect on the L-type Ca(2+) channels: facilitation and inhibition. Lower [Mg(2+)]i maintains and enhances the basal activity of Ca(2+) channels, whereas higher [Mg(2+)]i inhibits channel activity. Taken together, our data from the application of an [Mg(2+)]i series suggest that the dual effect of Mg(2+) upon the L-type Ca(2+) channels exhibits long open-time dependence.
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China.
authors.forename: Meimi
authors.initials: M
authors.lastname: Zhao
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Feng
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China.
authors.forename: Dongxue
authors.initials: D
authors.lastname: Shao
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China.
authors.forename: Shuyuan
authors.initials: S
authors.lastname: Liu
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Lei
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Sun
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Guo
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China.
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Hu
authors.affiliation: Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Kameyama
authors.affiliation: Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China. Electronic address: lyhao@mail.cmu.edu.cn.
authors.forename: Liying
authors.initials: L
authors.lastname: Hao
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002478:Cells, Cultured; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D015640:Ion Channel Gating / Q000187:drug effects; D008274:Magnesium / Q000494:pharmacology / Q000502:physiology*; D032342:Muscle Cells / Q000378:metabolism*; D018408:Patch-Clamp Techniques / Q000379:methods
chemical_list: D020746:Calcium Channels, L-Type; D008274:Magnesium
keywords: Ca(2+) channels; Inside-out configuration; Mg(2+); Open probability; Open time