Angiotensin II mediates uterine vasoconstriction through α-stimulation

Blair E. Cox, Timothy A. Roy, Charles R. Rosenfeld

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Intravenous angiotensin II (ANG II) increases uterine vascular resistance (UVR), whereas uterine intra-arterial infusions do not. Type 2 ANG II (AT 2) receptors predominate in uterine vascular smooth muscle; this may reflect involvement of systemic type 1 ANG II (AT1) receptor-mediated α-adrenergic activation. To examine this, we compared systemic pressor and UVR responses to intravenous phenylephrine and ANG II without and with systemic or uterine α-receptor blockade and in the absence or presence of AT1 receptor blockade in pregnant and nonpregnant ewes. Systemic α-receptor blockade inhibited phenylephrine-mediated increases in mean arterial pressure (MAP) and UVR, whereas uterine α-receptor blockade alone did not alter pressor responses and resulted in proportionate increases in UVR and MAP. Although neither systemic nor uterine α-receptor blockade affected ANG II-mediated pressor responses, UVR responses decreased >65% and also were proportionate to increases in MAP. Systemic AT1 receptor blockade inhibited all responses to intravenous ANG II. In contrast, uterine AT1 receptor blockade + systemic α-receptor blockade resulted in persistent proportionate increases in MAP and UVR. Uterine AT2 receptor blockade had no effects. We have shown that ANG II-mediated pressor responses reflect activation of systemic vascular AT1 receptors, whereas increases in UVR reflect AT1 receptor-mediated release of an α-agonist and uterine autoregulatory responses.

Original languageEnglish (US)
Pages (from-to)H126-H134
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume287
Issue number1 56-1
DOIs
StatePublished - Jul 1 2004

Keywords

  • Angiotensin receptors
  • Autoregulation
  • Blood pressure
  • Pregnancy
  • Uterine blood flow

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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