Abstract: AIMTo study the effects of rhBNP and milrinone on the cardiac hemodynamics and renal function in anesthetized dogs. METHODSThe actions of rhBNP given cumulatively iv 10,30 and 100 ng·kg^-1 for 30 min and milrinone of single dose (100 μg·kg^-1, iv) on cardiac hemodynamics and renal function were studied in anesthetized open-chest dogs. RESULTSIn anesthetized dogs (N=7) intravenous infusion of rhBNP at 10～100 ng·kg^-1, caused decreases in mean arterial pressure (MAP), left ventricular systolic pressure (LVSP), LVdP/d_tmax, pulmonary arterial pressure (PAP), left ventricular end diastolic pressure (LVEDP), total peripheral resistance (TPR) and renal vascular resistance (RVR) dose-dependently, without significant changes in cardiac output (CO), LV(dP/d_t)/P, renal blood flow (RBF) and heart rate (HR), increases in urinary volume and sodium excretion. In anesthetized dogs (N=6), there were remarkable decreases in MAP, LVEDP, PAP, TPR, RBF, RVR and urinary volume following the MIL (100 μg·kg^-1, iv), with significant increases of LVSP, ±LVdP/d_tmax, HR and CO, but no marked changes in urinary volume and sodium excretion. CONCLUSIONrhBNP reduces the pre-load and after-load in the anethetized dogs but showed no distinct effect on the contractility of the heart. Positive inotropic and chronotropic actions have been demonstrated after intravenous injection of milrinone 100 μg·kg^-1 in anesthetized dogs.