Sensitivity to angiotensin II of forearm resistance vessels in pregnancy.

Abstract

Resistance vessel sensitivity to angiotensin II in vivo was studied in 13 primigravid normotensive women (16-24 weeks gestation), and in 10 non-pregnant control women. Angiotensin II was infused into the brachial artery at doses of 10, 100, 1,000 and 10,000 fmol min-' and forearm blood flow measured by plethysmography. Reduction in forearm blood flow at all concentrations of angiotensin II was significantly greater in non-pregnant than in pregnant women. The dose-response relationships, plotted semi-logarithmically, were similar in shape in each group but sensitivity to angiotensin II was reduced in pregnant subjects compared with non-pregnant women. This is most simply explained by an effect of pregnancy on the sensitivity to angiotensin II of vascular smooth muscle in forearm resistance vessels.

Nitric oxide does not mediate the vasodilation of early human pregnancy

“…This is the first longitudinal study (of which we are aware) to investigate vascular reactivity in early ges­tation and after termination of pregnancy in the same women. The results from the present study show that baseline forearm blood flow is not elevated during first trimester, which is consistent with observations from previously reported studies 30,33 …”

“…It is possible that the fall of peripheral vascular resistance in early pregnancy might be caused by decreased vasoconstrictor effects. In fact, vascular sensitivity to angiotensin II may be reduced in the human forearm during pregnancy, although the renin‐angiotensin system is actually upregulated in early human ges­tation 3,30 . The plasma concentration of endothelin‐1, a second important vasoconstrictor molecule, is lower during pregnancy compared to non‐pregnant controls, whereas sensitivity to endothelin‐1 remains similar in isolated omental vessels 31,32 .…”

Endothelium-Dependent Relaxation and Angiotensin II Sensitivity in Experimental Preeclampsia

“…The contractile response to Ang-II was dramatically decreased in P-saline infused rats as compared to the NP rats, which is in line with a decreased blood flow reducing effect of Ang-II during human pregnancy [16]. Our data also confirm previous studies in the rat [72,73].…”

“…To study the role of the AT1-R and AT2-R in the blunted responsiveness to Ang-II during pregnancy [16], we studied the in-vitro responsiveness of the AT1-R and AT2-R to Ang-II in the rat. The contractile response to Ang-II was dramatically decreased in P-saline infused rats as compared to the NP rats, which is in line with a decreased blood flow reducing effect of Ang-II during human pregnancy [16].…”

“…While normal pregnancy is associated with a decreased sensitivity to the vasoconstrictor angiotensin II (Ang-II) [16], preeclampsia is associated with an increased response to Ang-II as compared to normal pregnancy [17]. During preeclampsia, the increased Ang-II sensitivity may even develop before the clinical manifestation of the disease [18,19].…”