title: The Effect of Dofetilide on the Heart Rate of GD11 and GD13 Rat Embryos, in vivo, Using Ultrasound.
abstract: BACKGROUND
  There are a wide range of drugs including antidepressants, anticonvulsants and antipsychotics that cause embryonic bradycardia in vitro but it is unknown if they have a similar effect in vivo. One way to verify whether these in vitro findings are replicated in vivo is by the use of ultrasound examination of dosed pregnant rats. We tested this by examining the effect of dofetilide on embryonic heart rate (HR) in vivo using ultrasound.
  
  
  METHODS
  Rats were dosed with dofetilide (4 or 2.5 mg/kg) on GD11 or (5 or 2.5 mg/kg) on GD13 and embryonic HR assessed by ultrasound, 2 and 24 hr later. Fetuses were examined for malformations on GD20.
  
  
  RESULTS
  HR of control rat embryos showed a wide range at each gestational day. Dosing with dofetilide on GD11 caused severe bradycardia (∼ 60% reduction) 2 hours after dosing with recovery after 24 h of >60% of LD but death and slow HR among the HD embryos. At term, 32% of the LD surviving fetuses had hypoplastic upper lip while >90% of HD embryos had died. On GD13, embryonic HR was reduced in a dose-dependent manner with >85% of LD and HD recovered by 24 hr. At term, all LD fetuses were normal while 29% of HD fetuses had limb defects.
  
  
  CONCLUSIONS
  Ultrasound is a useful technique to investigate the effect of maternally administered drugs on the embryonic HR in the rat. The results may provide more information about the safety of these drugs in pregnancy leading to better risk assessment for the human.
authors.affiliation: Discipline of Biomedical Science, University of Sydney, New South Wales, Australia.
authors.forename: Helen
authors.initials: H
authors.lastname: Ritchie
authors.affiliation: Discipline of Biomedical Science, University of Sydney, New South Wales, Australia.
authors.forename: Diana
authors.initials: D
authors.lastname: Oakes
authors.affiliation: Biological Resources Imaging Laboratory, University of New South Wales, New South Wales, Australia.
authors.forename: Tzong-tyng
authors.initials: TT
authors.lastname: Hung
authors.affiliation: Discipline of Biomedical Science, University of Sydney, New South Wales, Australia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hegedus
authors.affiliation: Discipline of Biomedical Science, University of Sydney, New South Wales, Australia.
authors.forename: Shreya
authors.initials: S
authors.lastname: Sood
authors.affiliation: Department of Anatomy and Histology, The University of Sydney, New South Wales, Australia.
authors.forename: William
authors.initials: W
authors.lastname: Webster
mesh_terms: D000818:Animals; D004622:Embryo, Mammalian / Q000187:drug effects* / Q000502:physiology*; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000187:drug effects*; D010627:Phenethylamines / Q000633:toxicity*; D051381:Rats; D013194:Staining and Labeling; D013449:Sulfonamides / Q000633:toxicity*; D016216:Ultrasonography, Prenatal / Q000379:methods*
chemical_list: D010627:Phenethylamines; D013449:Sulfonamides; C063533:dofetilide
keywords: embryo/fetal physiology; hypoxia; in vitro screens; pharmaceuticals; risk assessment