SINOAORTIC BAROREFLEX ACTIVITY AFFECTS ANGIOTENSIN SENSITIVITY IN NORMOTENSIVE WOMEN AT THE 20TH, BUT NOT AT THE 30TH, WEEK OF GESTATION

Objective: We examined the role of sinoaortic baroreflex activity in angiotensin II presser responsiveness in normotensive pregnant women. Methods: We performed angiotensin sensitivity testing in the 20th (n = 125) and 30th (n = 102) weeks of gestation. The effective presser dose of angiotensin II was defined as one that elicited a rise of 20 torr in the diastolic blood pressure. Baroreceptor reflex sensitivity was defined as the ratio of compensatory change in heart rate produced per unit change in mean arterial blood pressure in response to the infusion of angiotensin II. Results: The baroreceptor reflex sensitivity was significantly (P < 0.05) greater at the 20th week than at the 30th week of gestation. There was a significant correlation between baroreceptor reflex sensitivity and the effective presser dose of angiotensin II (r = -0.380, P < 0.001, n = 125). However, there was no correlation between the effective presser dose and baroreceptor reflex sensitivity at the 30th week. Conclusions: Activation of the baroreflex function acted as a circulatory buffer against angiotensin-induced hypertension in women at the 20th week of gestation. However, this reflex was diminished at the 30th week.