Pharmacological characterization of the activity of endogenous inotropic factor from porcine left ventricle.
We report some of the unique pharmacological properties of a semipurified endogenous inotropic factor (EIF) present in the extract of the porcine left ventricle. EIF produced the following effects: (a) increase in isometric contractile force developed by electrically driven canine right ventricular trabecula, reaching a maximum with 60-100 microliters/ml concentration; (b) inhibition of Na-pump activity in canine portal vein; (c) no digitalis-like cardiac toxicity, e.g., increased diastolic tension or spontaneous diastolic mechanical oscillatory activity, despite inhibition of the sodium pump; (d) a small increase in sarcoplasmic reticular Ca release from the heart but a large increase in transsarcolemmal Ca influx as seen in biphasic contractions, an action similar to that produced by digitalis-like substances; and (e) prolongation of the action potential duration and refractory period of the canine isolated trabeculae. This latter action may confer a unique antiarrhythmic property to EIF.
Chen
Q M
QM
Department of Pharmacology & Therapeutics, University of Manitoba, Winnipeg, Canada.
Chau
T
T
Agbanyo
M
M
Navaratnam
S
S
Khatter
J C
JC
Bose
D
D
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002316:Cardiotonic Agents / Q000302:isolation & purification / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D004285:Dogs; D004594:Electrophysiology; D006352:Heart Ventricles / Q000737:chemistry*; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D011169:Portal Vein / Q000187:drug effects; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D013552:Swine
D002316:Cardiotonic Agents; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium