title: Triclosan exposure reduces thyroxine levels in pregnant and lactating rat dams and in directly exposed offspring.
abstract: Thyroid disrupting chemicals can potentially disrupt brain development. Two studies investigating the effect of the antibacterial compound triclosan on thyroxine (T₄) levels in rats are reported. In the first, Wistar rat dams were gavaged with 75, 150 or 300 mg triclosan/kg bw/day throughout gestation and lactation. Total T₄ serum levels were measured in dams and offspring, and all doses of triclosan significantly lowered T₄ in dams, but no significant effects on T₄ levels were seen in the offspring at the end of the lactation period. Since this lack of effect could be due to minimal exposure through maternal milk, a second study using direct per oral pup exposure from postnatal day 3-16 to 50 or 150 mg triclosan/kg bw/day was performed. This exposure pointed to significant T₄ reductions in 16 day old offspring in both dose groups. These results corroborate previous studies showing that in rats lactational transfer of triclosan seems limited. Since an optimal study design for testing potential developmental neurotoxicants in rats, should include exposure during both the pre- and postnatal periods of brain development, we suggest that in the case of triclosan, direct dosing of pups may be the best way to obtain that goal.
authors.affiliation: National Food Institute, Technical University of Denmark, Division of Toxicology and Risk Assessment, Søborg, Denmark. maap@food.dtu.dk
authors.forename: Marta
authors.initials: M
authors.lastname: Axelstad
authors.forename: Julie
authors.initials: J
authors.lastname: Boberg
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Vinggaard
authors.forename: Sofie
authors.initials: S
authors.lastname: Christiansen
authors.forename: Ulla
authors.initials: U
authors.lastname: Hass
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000891:Anti-Infective Agents, Local / Q000008:administration & dosage / Q000009:adverse effects*; D001921:Brain / Q000187:drug effects / Q000196:embryology / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D052244:Endocrine Disruptors / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D047109:Fetal Development / Q000187:drug effects; D007774:Lactation; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects*; D009474:Neurons / Q000187:drug effects / Q000473:pathology; D020258:Neurotoxicity Syndromes / Q000097:blood / Q000151:congenital / Q000209:etiology / Q000473:pathology; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D017208:Rats, Wistar; D013961:Thyroid Gland / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D013974:Thyroxine / Q000097:blood* / Q000378:metabolism; D014260:Triclosan / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D000891:Anti-Infective Agents, Local; D052244:Endocrine Disruptors; D014260:Triclosan; D013974:Thyroxine
keywords: Developmental; Rat; Thyroid disrupting chemical (TDC); Thyroxine (T(4)); Triclosan