Magnesium sulfate and diphenylhydantoin relax canine middle cerebral artery contracted with the thromboxane-a2 analogue u46619 by different mechanisms: Implications for the management of eclampsia

Michael A. Belfort, George R. Saade, Kenneth J. Moise, Brian Kirshon, Paul M. Vanhoutte

Research output: Contribution to journalArticle

4 Scopus citations


Objectives: To investigate the relaxant effect of MgSO4 and diphenylhydantoin on isolated canine middle cerebral artery (MCA) rings contracted with the thromboxane-A2 analogue U46619. Methods: Canine MCA rings, with and without endothelium, were suspended in organ chambers for isometric tension recording. They were contracted with U46619 in the presence of indomethacin, with and without nitro-l-arginine (NLA). Cumulative dose-response curves were performed using MgSQ4 (10-8 M to 10-2 M) and diphenylhydantoin (10-9 M to 10-3 M). Main Outcome Measures: Tension at each concentration of the study drug expressed as a percentage of the maximum tension developed with U46619; area under the concentration response curve. Results: Both MgSO4 and diphenylhydantoin relaxed the MCA rings irrespective of the presence of endothelium. Diphenylhydantoin caused an endothelium-dependent relaxation at concentrations above 3 10-5 M, unaffected by NLA. Conclusions: MgSO4 relaxes canine MCA by a direct smooth muscle effect independent of the endothelium. Diphenylhydantoin causes an endothelium-dependent relaxation of canine MCA at concentrations above 3 10-5 M, unrelated to nitric oxide. MgSO4 and diphenylhydantoin may both help to prevent seizures in patients with eclampsia by reducing me potential for cerebral vasospasm.

Original languageEnglish (US)
Pages (from-to)51-60
Number of pages10
JournalHypertension in Pregnancy
Issue number1
StatePublished - Jan 1 1994



  • Cerebral vasospasm
  • Diphenylhydantoin
  • Magnesium sulfate

ASJC Scopus subject areas

  • Internal Medicine
  • Obstetrics and Gynecology

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