Positive Inotropic Effect of Helenalin, a Sesquiterpene Lactone, on Guinea-pig Myocardium

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Helenalin, a pseudoguaianolide sesquiterpene lactone which has hitherto been known as a potent antitumor and cytotoxic substance was found in this study to have a positive inotropic effect (PIE) on the myocardium. Left atrial strips and papillary muscles isolated from the guinea-pig heart were driven at a frequency of 1.0 Hz in Krebs-Henseleit solution at 30℃. Helenalin produced an increase in the force of contraction (Fc) depending on its concentration in the range between 10^<-5>-10^<-3>M. The potency of helenalin, expressed as pD_2 value, was 4.69 and 4.11 in the left atria and papillary muscle, respectively. The PIE of 3×10^<-4>M helenalin was equivalent to 78% of that of 10^<-5>M norepinephrine. The PIE of a higher concentration of helenalin (above 3×10^<-4>M) was neither affected by reserpinization nor by propranolol (3×10^<-5>M), but the PIE at lower concentrations was inhibited by reserpinization or propranolol. We conclude that the PIE of helenalin is produced in two different ways ; one is catecholamine-mediated and the other is an unknown direct effect.
公益社団法人日本薬学会の論文
1983-05-25