[Hemodynamic effects of infusions of alpha-human atrial natriuretic peptide in anesthetized dogs]

The purpose of this study is to investigate and compare the hemodynamic effects of infusion of alpha-human atrial natriuretic peptide (alpha-hANP) at three different doses. Mongrel dogs were anesthetized with 0.87% halothane in oxygen. alpha-hANP was infused for one hour with a constant rate at either 0.3, 1.0, or 10.0 micrograms.kg-1.min-1, respectively. They were randomly divided into four groups. Group A-1 received 0.3 micrograms.kg-1.min-1 of alpha-hANP; Group A-2 received 1.0 micrograms.kg-1.min-1 of alpha-hANP; Group A-3 received 10.0 micrograms.kg-1.min-1 of alpha-hANP; and Group C received normal saline as the vehicle and served as the control. Control values were obtained before infusion of alpha-hANP or vehicle was started, and hemodynamic variables were measured at 30 minutes intervals for two hours. Mean arterial pressure (MAP) of the group C showed no significant changes from control value. During and after infusion of alpha-hANP, MAP in the group A-2 and A-3 was significantly lower than the control values. The decrease in MAP of the group A-2 was the greatest. Heart rate decreased significantly at 60 minutes after termination of the infusion in all four groups. The reduction of cardiac index (CI) in the group-3 was the greatest. In the group A-3, it decreased for 31% from the control value at 60 minutes during infusion. However, this change was not significant. In contrast, the reduction in CI of the group A-2 was minimal. Mean pulmonary artery pressure (MPAP) of the group C showed no significant change from the control value. The patterns of changes in MPAP were similar to those of the alpha-hANP infused groups. It decreased progressively during the infusion. Systemic vascular resistance (SVR) was essentially unchanged in the group C. In the group A-2, SVR decreased slightly during the infusion period and then tended to increase after the infusion of alpha-hANP. In contrast, in the group A-1 and A-3, SVR increased progressively. The changes in left ventricular maximum dp/dt (LV dp/dt max) of the group C were minimal. The reduction in LV dp/dt max was more pronounced in group A-2 than in group A-3. In conclusion, our data show that hypotensive effects of alpha-hANP are associated with the reduction in cardiac output due to the decrease of cardiac contractility. However, the changes of hemodynamic variable are not dose-dependent.