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February 1, 1981Journal of Clinical InvestigationOpen Access

The chronically instrumental ewe: a model for studying vascular reactivity to angiotensin II in pregnancy.

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Population

Unanesthetized, chronically instrumented nonpregnant and pregnant sheep (68-143 days gestation)

Comparison

Continuous infusions of angiotensin II (AII) vs Nonpregnant sheep

Design

Preclinical

Authors

CRCharles R. RosenfeldThe University of Texas Southwestern Medical CenterNGN. F. GantThe University of Texas Southwestern Medical Center

Discussion

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Implication

Does not alter clinical hypertension management in pregnancy; extends validation of the pregnant ewe model for angiotensin II studies.

Key Points

  • This research aims to determine if the ewe can serve as a model for studying vascular responses to angiotensin II during pregnancy.
  • Studied unanesthetized, chronically instrumented nonpregnant and pregnant sheep at 68-143 days gestation.
  • Established dose-response curves for mean arterial pressure and uterine blood flow in all subjects.
  • Conducted continuous infusions of angiotensin II and measured corresponding physiological responses.
  • Pregnant ewes required a significantly higher dose of angiotensin II (0.016 mcg/min/kg) than nonpregnant ewes (0.009 mcg/min/kg) to achieve a 20 mm HG rise in mean arterial pressure (P<0.001).
  • There was a distinct difference in the slope and intercept of regression lines for the pressor response between pregnant and nonpregnant ewes (P<0.001).
  • In pregnant ewes, uterine blood flow increased at lower doses of angiotensin II, while higher doses led to a reduction in blood flow.

Structured PICO

P
Population
Unanesthetized, chronically instrumented nonpregnant and pregnant sheep (68-143 days gestation)
I
Intervention
Continuous infusions of angiotensin II (AII)
C
Comparator
Nonpregnant sheep
O
Outcome
Changes in mean arterial pressure and uterine blood flowsurrogate

The chronically instrumented ewe serves as a suitable animal model for studying the unique pregnancy-modified systemic and uteroplacental vascular refractoriness to angiotensin II.

Cite This Study

Rosenfeld et al. (1981) studied this question.

synapsesocial.com/papers/6a22688f00d432b2e190fe3dhttps://doi.org/10.1172/jci110057
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Also Consider

Synapse has enriched 4 closely related papers on similar clinical questions. Consider them for comparative context:

  1. 1A Study of Angiotensin II Pressor Response throughout Primigravid Pregnancy1973 · 1,231 citations
  2. 2Uterine blood flow and uterine renin secretion1972 · 105 citations
  3. 3Regional Flow-Pressure Relationship in Response to Angiotensin in the Intact Dog and Sheep1961 · 57 citations
  4. 4Effect of Prostaglandin Synthetase Inhibitors on Pressor Response to Angiotensin II in Human Pregnancy*1978 · 154 citations