Effects of Intraduodenal Administration of "Kyushin," a Senso (Toad Venom)-Containing Drug, on Systemic Hemodynamics, CardiacFunction 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 administration of KY in anesthetized open-chest dogs. KY (3 or 10 mg/kg) dose-dependently increased the peak positive first derivative of left ventricular pressure ((+)LVdP/dt) and mean aortic pressure, and decreased the left ventricular end-diastolic pressure (LVEDP). Myocardial oxygen consumption (MVO2) and heart rate (HR) were not significantly influenced 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 concentrations 20 min after administration of 3 and 10 mg/kg KY were dose-dependent. From the relationship between changes in (+)LVdP/dt and changes in BRS concentration after administration of KY, it is inferred that the effective concentration of BRS in plasma at which KY produces a cardiotonic effect in dogs is approximately 2-3 ng/ml.