Systemic and uterine responses to α-adrenergic stimulation in pregnant and nonpregnant ewes

R. R. Magness, C. R. Rosenfeld

Research output: Contribution to journalArticle

90 Citations (Scopus)

Abstract

Attenuated systemic pressor responses to infused angiotensin II characterize normal human and ovine pregnancy; moreover, uterine vascular refractoriness is greater than that of the systemic vasculature overall. It remains unclear whether this generalized refractoriness also pertains to other vasoconstrictors; therefore we studied simultaneous systemic and uterine responses to α-agonists in pregnant (n = 6) and nonpregnant (n = 6) sheep. Mean arterial pressure, heart rate, uterine blood flow, and cardiac output were measured before and during infusions of norepinephrine (0.456 to 45.84 μg/min) and phenylephrine (1.29 to 129 μg/min). Both α-agonists caused dose-dependent increases (p < 0.01) in mean arterial pressure and systemic vascular resistance and decreases in cardiac output (p < 0.01) in nonpregnant and pregnant animals; however, nonpregnant pressor responses exceeded pregnant ones. Nonpregnant ewes also had greater decreases in uterine blood flow (p < 0.05) and increases in uterine vascular resistance (p < 0.05); furthermore, increases in uterine vascular resistance exceeded those of systemic vascular resistance in both groups (p < 0.01). Attenuated uterine and systemic responses to α-agonists characterize normal ovine pregnancy; however, in contrast to the results with angiotensin II, the uterine vascular bed is substantially more responsive to α-agonists than the systemic vasculature overall.

Original languageEnglish (US)
Pages (from-to)897-904
Number of pages8
JournalAmerican Journal of Obstetrics and Gynecology
Volume155
Issue number4
StatePublished - 1986

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Vascular Resistance
Adrenergic Agents
Sheep
Angiotensin II
Cardiac Output
Blood Vessels
Arterial Pressure
Pregnancy
Phenylephrine
Vasoconstrictor Agents
Norepinephrine
Heart Rate

ASJC Scopus subject areas

  • Medicine(all)
  • Obstetrics and Gynecology

Cite this

Systemic and uterine responses to α-adrenergic stimulation in pregnant and nonpregnant ewes. / Magness, R. R.; Rosenfeld, C. R.

In: American Journal of Obstetrics and Gynecology, Vol. 155, No. 4, 1986, p. 897-904.

Research output: Contribution to journalArticle

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