title: Effect of acetylstrophanthidin on action potential duration and relation with extracellular potassium in sheep isolated Purkinje fibers.
abstract: OBJECTIVE
  To study the relation between the effect of acetylstrophanthidin on action potential duration (APD) and the extracellular potassium concentration.
  
  
  METHODS
  Effect of acetylstrophanthidin (AS 0.15 mmol.L-1) on APD at different extracellular potassium concentrations was studied at the stimulation cycle lengths of 990 and 690 ms in sheep isolated cardiac Purkinje fibers using the standard microelectrode technique.
  
  
  RESULTS
  At [K+]o 4.0 mmol.L-1, the biphasic effect of AS on APD appeared obviously. Both APD50 and APD90 were lengthened within the first 10 min of drug exposure. After 10 min, they were shortened at all pacing cycle lengths. On the other hand, at [K+]o 5.4 mmol.L-1, AS only shortened APD markedly without lengthening effect on it. The biphasic and monophasic effects of AS on APD were found at [K+]o 4.0 mmol.L-1 and 5.4 mmol.L-1, respectively.
  
  
  CONCLUSIONS
  The effect of AS on APD was related to the concentration of [K+]o.
authors.affiliation: Department of Medicine, University of Chicago, IL 60637, USA. weichen@UIC.EDU
authors.forename: J T
authors.initials: JT
authors.lastname: Xie
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.forename: P M
authors.initials: PM
authors.lastname: Cunningham
authors.forename: C T
authors.initials: CT
authors.lastname: January
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D066298:In Vitro Techniques; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism*; D011690:Purkinje Fibers / Q000166:cytology / Q000502:physiology*; D013327:Strophanthidin / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D013327:Strophanthidin; C004681:acetylstrophanthidin; D011188:Potassium