Paper Information

Title: 

MYOCARDIAL EFFECTS OF HAWTHORN EXTRACTS IN CULTURED NEONATAL MURINE CARDIOMYOCYTE

Type: SPEECH
Author(s): SALAHI S.*,LONG SH.R.,CROFOOT K.,PROTEAU PH.,FILTZ T.H.M.
 
 *
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2007Volume 18
 
 
Abstract: 

Different species of Crataegus commonly called hawthorn, were reported to possess wide pharmacological properties on the cardiovascular system. Preparations of hawthorn are used in coronary heart disease, heart failure and cardiac arrhythmia. It was shown that hawthorn causes negative chronotropic and positive inotropic effects in isolated cardiomyocytes which are not due to beta- adrenergic receptor inhibition or stimulation, respectively. To test the hypothesis that hawthorn is acting via muscarinic receptors, we investigated the binding affinity of a partially purified hawthorn extract fraction to M2 muscarinic receptor of mouse heart membranes using [³H]QNB, a high affinity muscarinic receptor antagonist, as a radioligand. Hawthorn extract fraction 3 dose-dependently inhibited [³H]QNB binding to mouse heart membranes. We demonstrated that hawthorn extracts cause a negative chronotropic effect on both atrial and ventricular cardiomyocytes, although the effects were greater in atrial than ventricular cardiomyocytes. The similarity of hawthorn's effect to that of the muscarinic agonist carbachol was investigated by determining the effect of atropine (non-selective) and himbacine (selective), M2 receptor antagonists, on the chronotropic response of atrial and ventricular cardiomyocytes to hawthorn extracts. The muscarinic antagonists significantly blocked the negative chronotropic effect of hawthorn extracts. In addition, we determined the effects of hawthorn on inositol phosphate (InsP)- formation in neonatal mice cardiomyocytes (assessed as accumulation of total [³H]-InsP in myo-[³H]-inositol pre-labelled cells). In isolated ventricular cardiomyocytes of neonatal mice, hawthorn extract caused a concentration-dependent increase in [³H]-inositol phosphate (InsP) formation suggesting that the positive inotropic effect of hawthorn may closely related to the InsP formation. We are attempting to isolate the negative chronotropic and positive inotropic components of hawthorn extracts.

 
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