Large conductance Ca2+-activated K+ channels modulate uterine α1-adrenergic sensitivity in ovine pregnancy

Charles R. Rosenfeld, Linda S. Hynan, Xiao Tie Liu, Timothy Roy

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

The uteroplacental vasculature is refractory to α-adrenergic stimulation, and large conductance Ca2+-activated K+ channels (BKCa) may contribute. We examined the effects of uterine artery (UA) BKCa inhibition with tetraethylammonium (TEA) on hemodynamic responses to phenylephrine (PE) at 101 to 117 days and 135 to 147 days of ovine gestation, obtaining dose responses for mean arterial pressure (MAP), heart rate (HR), and uteroplacental blood flow (UPBF) and vascular resistance (UPVR) before and during UA TEA infusions. The UA α1-adrenergic receptors (α1-ARs) were assessed. The PE increased MAP and UPVR and decreased HR and UPBF dose dependently at both gestations (P <.001, analysis of variance). The %δMAP was less at 135 to 147 days before and during TEA infusions (P ≤.008); however, responses during TEA were greater (P ≤.002). The PE increased %δUPVR>>%δMAP, thus %δUPBF fell. The TEA enhanced PE-mediated increases in %δUPVR at 135 to 147 days (P ≤.03). The UA α1-AR expression was unchanged in pregnancy. Uterine vascular responses to PE exceed systemic vascular responses throughout pregnancy and are attenuated by BKCa activation, suggesting BKCa protect UPBF.

Original languageEnglish (US)
Pages (from-to)456-464
Number of pages9
JournalReproductive Sciences
Volume21
Issue number4
DOIs
StatePublished - Apr 2014

Keywords

  • pressor responses
  • uteroplacental blood flow
  • vascular sensitivity

ASJC Scopus subject areas

  • Obstetrics and Gynecology

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