title: Subclinical effects of prenatal methylmercury exposure on cardiac autonomic function in Japanese children.
abstract: OBJECTIVE
  The subclinical effects of prenatal exposure to methylmercury from fish consumption on the cardiac autonomic function were assessed in 136 Japanese 7-year-old children recruited for this study.
  
  
  METHODS
  Samples of child's hair and dry umbilical cord preserved were collected, and hair mercury and cord tissue methylmercury concentrations were determined as current and prenatal exposure biomarkers, respectively. Cardiac autonomic indicators of parasympathetic and sympathetic activities were calculated from the electrocardiographic RR intervals measured.
  
  
  RESULTS
  In the children, the cord tissue methylmercury (0.017-0.367, median 0.089 microg/g) was not significantly correlated with the hair mercury (0.43-6.32, median 1.66 microg/g). The cord tissue methylmercury was related negatively to parasympathetic components of cardiac autonomic indicators (P < 0.05) and positively to sympathovagal indices (P < 0.05), even after correction for possible confounders such as age and sex, although the hair mercury was not significantly correlated with any cardiac autonomic indicators.
  
  
  CONCLUSIONS
  Despite the potential limitations involved in the retrospective study, these findings suggest that prenatal methylmercury exposure (median of estimated maternal hair mercury at parturition, 2.24 microg/g) may be associated with reduced parasympathetic activity and/or sympathovagal shift.
authors.affiliation: Department of Environmental Health Sciences, Akita University School of Medicine, 010-8543, Akita, Japan. winestem@med.akita-u.ac.jp
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Murata
authors.forename: Mineshi
authors.initials: M
authors.lastname: Sakamoto
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Nakai
authors.forename: Miwako
authors.initials: M
authors.lastname: Dakeishi
authors.forename: Toyoto
authors.initials: T
authors.lastname: Iwata
authors.forename: Xiao-Jie
authors.initials: XJ
authors.lastname: Liu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Satoh
mesh_terms: D000818:Animals; D001341:Autonomic Nervous System / Q000503:physiopathology*; D002302:Cardiac Output / Q000502:physiology*; D002648:Child; D004562:Electrocardiography; D004781:Environmental Exposure; D005260:Female; D005399:Fishes / Q000382:microbiology; D006197:Hair / Q000382:microbiology; D006801:Humans; D007564:Japan; D008297:Male; D018811:Maternal Exposure; D008767:Methylmercury Compounds / Q000032:analysis / Q000493:pharmacokinetics*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012189:Retrospective Studies; D014873:Water Pollutants
chemical_list: D008767:Methylmercury Compounds; D014873:Water Pollutants