(Hypertension. 1997;30:1247-1252.)
© 1997 American Heart Association, Inc.
Articles |
From the Department of Obstetrics and Gynecology, D Floor, East Block, Queen's Medical Centre, University Hospital, Nottingham, NG7 2 UH England.
Correspondence to F. Broughton Pipkin, Professor of Perinatal Physiology, Department of Obstetrics and Gynaecology, D Floor, East Block, Queen's Medical Centre, University Hospital, Nottingham, NG7 2UH, England. E-mail Fiona.Broughton-Pipkin{at}nottingham.ac.uk
Abstract Studies in anesthetized animals suggest that
angiotensin II evokes a depressor as well as a pressor
effect, which becomes evident on cessation of infusion. We have studied
18 nonpregnant and 8, 23, and 22 women in the first, second, and third
trimesters of pregnancy to determine whether such an effect is
present in conscious women, whether it is dose dependent, and
whether it is influenced by pregnancy. Angiotensin II was
infused intravenously in doubling concentrations at
10-minute intervals until a pressor effect of
20 mm Hg was
observed. The infusion was stopped, and blood pressure was monitored at
2-minute intervals for 30 minutes. There was a significant
diastolic depressor effect after stopping
angiotensin II in the nonpregnant women and those in the
second and third trimesters of pregnancy. Individual women required
differing doses of angiotensin II to evoke the standardized
pressor response. It was thus possible to examine the depressor
response in each group in relation to infused doses of
angiotensin II. In nonpregnant women and in those in the
second and third trimesters of pregnancy, the depressor response was
dose dependent (P<.001). At any given dose, the depressor
response deepened as pregnancy progressed (P<.001). Basal
plasma prostacyclin concentrations rise in pregnancy, and
angiotensin II can stimulate prostacyclin synthesis. This
might mediate the depressor effect. In conclusion, the diminished
pressor response to angiotensin II in normal pregnancy may
be partly due to an increasing depressor effect of the hormone.
Key Words: angiotensin II renin-angiotensin system blood pressure pregnancy, humans
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