title: Relationship between cardiotonic effects and inhibition on cardiac sarcolemmal Na+,K+-ATPase of strophan-thidin at low concentrations.
abstract: OBJECTIVE
  To evaluate the effects of strophanthidin (Str) on cardiac contractile function and sarcolemmal Na+, K+-ATPase activities in isolated guinea-pig hearts.
  
  
  METHODS
  Isolated guinea-pig hearts were perfused through aorta in a Langendorff mode. Heart rate (HR), left ventricular pressure (LVP), and first derivatives (+/-dp/dt(max)) of LVP were recorded by eight-channel physiological instrument. Cardiac sarcolemmal Na+, K+-ATPase activities were determined with colorimetry.
  
  
  RESULTS
  Str 0.1 nmol/L stimulated the Na+, K+-ATPase activities (P<0.05), but had no effect on HR, LVP, and +/-dp/dt(max). Str 1 nmol/L increased +dp/dt(max) (P<0.05) and Na+, K+-ATPase activities (P<0.01). Str 10 and 100 nmol/L significantly increased both LVP (P<0.05) and +dp/dt(max) (P<0.05 or P<0.01), and had no significant effects on Na+, K+-ATPase activities. However, Str 1-100 micromol/L at first enhanced the LVP and +dp/dtmax (P<0.01), then reduced them resulting from irregular contraction, and effects of Str on Na+, K+-ATPase activities revealed a concentration-dependent inhibition (P<0.01).
  
  
  CONCLUSIONS
  The positive inotropic effects and irregular contraction produced by Str at higher concentrations result from the inhibition of Na+, K+-ATPase activities, and the positive inotropic effects of Str at lower concentrations are not related to the inhibition of the Na+, K+-ATPase activities.
authors: Department of Pharmacology, School of Basic Medicine, Hebei Medical University, Shijiazhuang 050017, China.
authors: Su-Wen
authors: SW
authors: Su
authors: Yong-Li
authors: YL
authors: Wang
authors: Jun-Xia
authors: JX
authors: Li
authors: He-Shan
authors: HS
authors: Mei
authors: Jing-Xiang
authors: JX
authors: Yin
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002316:Cardiotonic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D012508:Sarcolemma / Q000201:enzymology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013327:Strophanthidin / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D002316:Cardiotonic Agents; D013327:Strophanthidin; D000254:Sodium-Potassium-Exchanging ATPase