Angiotensin II and α-agonist. II. Effects on ovine fetoplacental prostaglandins

T. Yoshimura, R. R. Magness, C. R. Rosenfeld

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The fetoplacental vasculature is more sensitive to angiotensin II (ANG II) than to α-agonists, possibly reflecting their differing effects on vascular prostaglandin (PG) production. To examine this we studied in fetal sheep (123-138 days) the effects of ANG II (n = 7; 0.057, 1.15, and 5.73 μg/min) and phenylephrine (PHEN, n = 7; 0.306, 1.53, and 7.64 μg/min) on mean arterial pressure (MAP), heart rate (HR), and simultaneous measurements of umbilical arterial and venous PGE2, 6-keto-PGF(1α) (PGI2) and thromboxane B2 (TxB2) concentrations. ANG II increased MAP and decreased HR dose dependently (P<0.05). Basal umbilical venous plasma PGE2 levels exceeded PGI2 (P<0.001) and increased during ANG II infusions from 502 ± 63 to 516 ± 113,647 ± 188, and 1,968 ± 541 pg/ml (mean ±SE, P<0.05), as did venous-arterial concentration differences (129 ± 26 to 179 ± 47, 244 ± 58, and 1,287 ± 507 pg/ml, respectively; P<0.05). ANG II also increased umbilical venous PGI2 levels from 110 ± 13 to 116 ± 24, 144 ± 46, and 680 ± 147 pg/ml (P<0.01) and the venous-arterial concentration difference from 3 ± 6 to 20 ± 16, 41 ± 27, and 405 ± 122 pg/ml (P<0.05), respectively. ANG II had no effect on plasma TxB2, and no umbilical venous-arterial concentration differences existed. Although PHEN increased MAP and decreased HR, plasma eicosanoid concentrations were unaltered. The fetus is more sensitive to ANG II than PHEN; however, only ANG II increased placental PGE2 and PGI2 production. It is unlikely that local prostanoid production explains the observed refractoriness to α-adrenergic stimulation.

Original languageEnglish (US)
Pages (from-to)H473-H479
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume259
Issue number2 28-2
StatePublished - 1990

Keywords

  • phenylephrine
  • placenta
  • pregnancy
  • prostacyclin
  • prostaglandi n E
  • thromboxane

ASJC Scopus subject areas

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

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