title: Effects of neferine on Kv4.3 channels expressed in HEK293 cells and ex vivo electrophysiology of rabbit hearts.
abstract: OBJECTIVE
  Neferine is an isoquinoline alkaloid isolated from seed embryos of Nelumbo nucifera (Gaertn), which has a variety of biological activities. In this study we examined the effects of neferine on Kv4.3 channels, a major contributor to the transient outward current (I(to)) in rabbit heart, and on ex vivo electrophysiology of rabbit hearts.
  
  
  METHODS
  Whole-cell Kv4.3 currents were recorded in HEK293 cells expressing human cardiac Kv4.3 channels using patch-clamp technique. Arterially perfused wedges of rabbit left ventricles (LV) were prepared, and transmembrane action potentials were simultaneously recorded from epicardial (Epi) and endocardial (Endo) sites with floating microelectrodes together with transmural electrocardiography (ECG).
  
  
  RESULTS
  Neferine (0.1-100 μmol/L) dose-dependently and reversibly inhibited Kv4.3 currents (the IC50 value was 8.437 μmol/L, and the maximal inhibition at 100 μmol/L was 44.12%). Neferine (10 μmol/L) caused a positive shift of the steady-state activation curve of Kv4.3 currents, and a negative shift of the steady-state inactivation curve. Furthermore, neferine (10 μmol/L) accelerated the inactivation but not the activation of Kv4.3 currents, and markedly slowed the recovery of Kv4.3 currents from inactivation. Neferine-induced blocking of Kv4.3 currents was frequency-dependent. In arterially perfused wedges of rabbit LV, neferine (1, 3, and 10 μmol/L) dose-dependently prolonged the QT intervals and action potential durations (APD) at both Epi and Endo sites, and caused dramatic increase of APD10 at Epi sites.
  
  
  CONCLUSIONS
  Neferine inhibits Kv4.3 channels likely by blocking the open state and inactivating state channels, which contributes to neferine-induced dramatic increase of APD10 at Epi sites of rabbit heart.
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Yu-fang
authors.initials: YF
authors.lastname: Chen
authors.affiliation: Department of Geriatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Xiao-qing
authors.initials: XQ
authors.lastname: Quan
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Jun-hua
authors.initials: JH
authors.lastname: Xiao
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Jia-ling
authors.initials: JL
authors.lastname: Wang
authors.affiliation: Department of Geriatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Cun-tai
authors.initials: CT
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Ji-zhou
authors.initials: JZ
authors.lastname: Xiang
authors.affiliation: Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Tang
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D044182:Benzylisoquinolines / Q000494:pharmacology*; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D057809:HEK293 Cells; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D018408:Patch-Clamp Techniques; D011817:Rabbits; D051672:Shal Potassium Channels / Q000378:metabolism*
chemical_list: D044182:Benzylisoquinolines; D004365:Drugs, Chinese Herbal; D051672:Shal Potassium Channels; C057222:neferine