title: Glycyrretinic acid blocks cardiac sodium channels expressed in Xenopus oocytes.
abstract: BACKGROUND
  Licorice has been used to treat many ailments including cardiovascular disorders in China for long time. Recent studies have shown that the cardiac actions of licorice have been attributed to its active component, glycyrretinic acid (GA). However, its mechanism remains poorly understood.
  
  
  OBJECTIVE
  The effects of GA on the cardiac sodium currents (I(Na)), L-type calcium currents (I(Ca,L)) and hyperpolarization-activated inward currents (I(f)) were investigated.
  
  
  METHODS
  Human isoforms of wild-type and DeltaKPQ-mutant type sodium channels were expressed in Xenopus oocytes, and the resulting currents (peak and late I(Na)) were recorded using a two-microelectrode voltage-clamp technique. A perforated patch clamp technique was employed to record I(Ca,L) and I(f) from isolated rabbit sinoatrial node pacemaker cells.
  
  
  RESULTS
  GA inhibited peak I(Na) (33% at 90 microM) and late I(Na) (72% at 90 microM), but caused no significant effects on I(Ca,L) and I(f).
  
  
  CONCLUSIONS
  GA blocked cardiac sodium currents, particularly late I(Na.) Our findings might help to understand the traditional use of licorice in the treatment of cardiovascular disorders, because reduction of sodium currents (particularly late I(Na)) would be expected to provide protection from Na(+)-induced Ca(2+) overload and cell damage.
authors: Ion Channelopathy Research Center, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, PR China.
authors: Yimei
authors: Y
authors: Du
authors: Songyu
authors: S
authors: Zhang
authors: Hongjin
authors: H
authors: Wu
authors: Anruo
authors: A
authors: Zou
authors: Ming
authors: M
authors: Lei
authors: Longxian
authors: L
authors: Cheng
authors: Yuhua
authors: Y
authors: Liao
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000187:drug effects; D006034:Glycyrrhetinic Acid / Q000494:pharmacology*; D006035:Glycyrrhiza / Q000737:chemistry*; D006321:Heart / Q000187:drug effects*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D008564:Membrane Potentials; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010936:Plant Extracts / Q000494:pharmacology*; D011817:Rabbits; D012849:Sinoatrial Node / Q000166:cytology; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000187:drug effects* / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D020746:Calcium Channels, L-Type; D010936:Plant Extracts; D015222:Sodium Channels; D012964:Sodium; D006034:Glycyrrhetinic Acid; D002118:Calcium