EFFECTS OF INTRADUODENAL ADMINISTRATION OF KYUSHIN, A SENSO (TOAD VENOM)-CONTAINING DRUG, ON SYSTEMIC HEMODYNAMICS, CARDIAC-FUNCTION AND MYOCARDIAL OXYGEN-CONSUMPTION IN ANESTHETIZED DOGS

The effects of ''Kyushin'' (KY), a Senso (toad venom)-containing drug, on the cardiovascular system were examined by intraduodenal administr ation of KY in anesthetized open-chest dogs. KY (3 or 10 mg/kg) dose-d ependently increased the peak positive first derivative of left ventri cular pressure ((+)LVdP/dt) and mean aortic pressure, and decreased th e left ventricular end-diastolic pressure (LVEDP). Myocardial oxygen c onsumption (MVO2) and heart rate (HR) were not significantly influence d by KY. KY produced a cardiotonic effect without any increase in MVO2 , because the increase in MVO2 due to the cardiotonic effect of KY may have been cancelled by a decrease in MVO2 due to reduction of preload and the lack of increase in HR. In order to clarify the relationship between the cardiovascular effects of KY and the drug concentration in plasma, the concentration of anti-bufalin IgG reactive substance (BRS ) in plasma was measured by enzyme immunoassay. The maximum BRS concen trations 20 min after administration of 3 and 10 mg/kg KY were dose-de pendent. From the relationship between changes in (+)LVdP/dt and chang es in BRS concentration after administration of KY, it is inferred tha t the effective concentration of BRS in plasma at which KY produces a cardiotonic effect in dogs is approximately 2-3 ng/ml.