Cardiotonic effect of Apocynum venetum L. extracts on isolated guinea pig atrium.
The effects on guinea-pig heart muscle of extracts of Apocynum venetum L. leaf, root, stem, old stem and Venetron--a polyphenol-rich extract of leaves--were studied by recording the mechanical activity and heart rate of isolated right atria. Cymarin--a cardiac glycoside--was also determined in A. venetum extracts by LC-MS/MS analysis. All extracts examined here showed a weak cardiotonic effect, i.e., induced a contractile response of the isolated atria and increased the pulse at a concentration of 1 mg/mL, which was not inhibited by propranolol (1 microM)-a beta-adrenoceptor blocker. The cymarin content in extracts of A. venetum was ranked as follows: old stem >> stem > root > leaf >> Venetron. Since the cardiotonic effects of A. venetum extracts did not reflect the cymarin content, a possible mechanism other than that of cardiac glycosides was investigated. The inhibitory effects on phosphodiesterase 3 (PDE3) were studied in a cell-free enzyme assay; all extracts of various parts of A. venetum inhibited PDE purified from human platelets. These results suggest that PDE3 inhibition may contribute to the cardiotonic effects of A. venetum extracts.
Irie
Kaoru
K
Faculty of Pharmacy and Research Institute of Pharmaceutical Sciences, Musashino University, 1-1-20 Shinmachi, Nishitokyo, Tokyo, Japan. k_irie@musashino-u.ac.jp
Sato
Takahiro
T
Tanaka
Ippei
I
Nakajima
Jun-ichiro
J
Kawaguchi
Maiko
M
Himi
Toshiyuki
T
D000818:Animals; D030010:Apocynum / Q000737:chemistry*; D002316:Cardiotonic Agents / Q000302:isolation & purification / Q000494:pharmacology*; D002853:Chromatography, Liquid; D003529:Cymarine / Q000302:isolation & purification / Q000494:pharmacology; D006168:Guinea Pigs; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D058987:Phosphodiesterase 3 Inhibitors; D010726:Phosphodiesterase Inhibitors / Q000302:isolation & purification / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology*; D053719:Tandem Mass Spectrometry
D002316:Cardiotonic Agents; D058987:Phosphodiesterase 3 Inhibitors; D010726:Phosphodiesterase Inhibitors; D010936:Plant Extracts; D003529:Cymarine