A reduced pressor response to infused angiotensin II has been observed in pregnancy. Although this has been considered to reflect reduced sensitivity of the peripheral vasculature to angiotensin II, it has also been suggested that the reduced pressor response is due to a fall in cardiac output during infusion of angiotensin II in pregnancy. In the present study we investigated the hemodynamic responses to infused angiotensin II in chronically instrumented, pregnant and nonpregnant sheep. We measured changes in cardiac output and systemic vascular resistance and related these changes to the increase in mean arterial pressure. The response in systemic vascular resistance to angiotensin II was substantially reduced in pregnant sheep. During angiotensin II infusion cardiac output fell in both groups, but the effect of the fall in cardiac output in reducing the pressor response was greater in nonpregnant animals. Thus, it appears that the reduced pressor response to angiotensin II in pregnant sheep is due to reduced systemic vascular responsiveness and not to differences in cardiac output responses.
ASJC Scopus subject areas
- Obstetrics and Gynecology