Referenced in: none

Automatically associated channels: Kv2.1

Title: The inhibitory effect of shakuyakukanzoto on K+ current in H9c2 cells.

Authors: Azusa Suganami, Kazuho Sakamoto, Tomoyuki Ono, Hirotake Watanabe, Nahoko Hijioka, Masahiro Murakawa, Junko Kimura

Journal, date & volume: Fukushima J Med Sci, 2014 , 60, 22-30

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/24670676

Abstract
Shakuyakukanzoto (shao-yao-gan-cao-tang) is a commonly used Chinese traditional herbal medicine for the treatment of acute pain with muscle cramp. However, its mechanism of action is unclear. We previously reported that a low concentration of Kanzo (licorice) and isoliquiritigenin, a component of licorice, inhibited the potassium (K(+)) current in H9c2 cells. Therefore, in the present study, we examined the effects of Shakuyakukanzoto, Shakuyaku or Kanzo on the K(+) current (IKur) in H9c2 cells. Shakuyakukanzoto inhibited IKur in a concentration-dependent manner. The half-maximal concentration of Shakuyakukanzoto was approximately 1.3 mg/mL and the Hill coefficient was 1.2. The order of potency of inhibiting IKur was Kanzo>Shakuyakukanzoto>Shakuyaku. Glycyrrhizin, a major component of licorice, had no inhibitory effect on IKur. A small interfering RNA experiment indicated that IKur was most likely to be Kv2.1 in H9c2 cells. Our results suggest that Shakuyakukanzoto may normalize intracellular and extracellular K(+) balance by inhibiting IKur and reducing K(+) efflux, while the Na(+)-K(+) pump promotes K(+) influx into myofibers. Consequently, excess K(+) may be reduced from external space of myofibers. This may be a part of the Shakuyakukanzoto mechanism for improving muscle pain.