title: Inhibitory effect of potassium alum on smooth muscle contraction of rabbit and its mechanism.
abstract: OBJECTIVE
  To investigate the effects of potassium alum (Alunite) on smooth muscle contraction and phosphorylation of myosin light chain by myosin light chain kinase (MLCK) and to try to find out the clue of its mechanism.
  
  
  METHODS
  An isolated rabbit duodenum smooth muscle strip was selected to study the effects of potassium alum on its contractile activity under the condition of Krebs' solution using HW-400S constant temperature smooth muscle trough. The myosin and MLCK were purified from chicken gizzard smooth muscle. Myosin light chain phosphorylation was determined by glycerol-polyacrylamide gel electrophoresis; myosin Mg2+-ATPase activity was measured by inorganic phosphate liberation method.
  
  
  RESULTS
  Potassium alum (2.5-20 mmol/L) inhibited the contraction on duodenum in a dose-related and a time-dependent manner; potassium alum could also inhibit the extent of phosphorylation of myosin light chain in a dose-related and a time-dependent manner; and potassium alum inhibited the extent of Mg2+-ATPase activity in a dose-related manner.
  
  
  CONCLUSIONS
  Potassium alum inhibited smooth muscle contraction in a way of inhibiting phosphorylation of myosin light chain and Mg2+-ATPase activity. This has revealed the molecular mechanism of treatment of gastrointestinal spastic disorders by potassium alum.
authors.affiliation: Department of Pharmacology, Dalian Medical University, Dalian, Liaoning Province, 116044, China.
authors.forename: Zhong-Yuan
authors.initials: ZY
authors.lastname: Tang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Lin
authors.forename: Xiao-Li
authors.initials: XL
authors.lastname: Yang
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Ze-Yao
authors.initials: ZY
authors.lastname: Tang