title: Susceptibility of newborn rats to 3-ethylphenol and 4-ethylphenol compared with that of young rats.
abstract: Newborn rat studies were conducted with oral administration of 3-ethylphenol (3EP) and 4-ethylphenol (4EP) on postnatal days (PND) 4-21 to allow comparison of no observed adverse effect level (NOAEL) and unequivocally toxic level (UETL) with those from 28-day studies of young rats starting at 5-6 weeks of age. In the newborn rat studies, slightly lowered body weight was observed after 3EP treatment, and deaths, hypoactivity, Straub tail, deep respiration and delayed righting reflex were clearly observed after 4EP treatment. In the young rat studies, salivation, staggering gait, changes in the liver including high values of liver weight and alanine aminotransferase or total cholesterol and the lesions in the forestomach were clearly observed after 3EP and 4EP treatments. NOAELs of 3EP and 4EP in the newborn rat studies appeared to be almost 3 times lower than those in the young rat studies. As a clear toxicity of 3EP was not observed in newborn rats, UETLs were not established for 3EP. Regarding 4EP, UETL of young rats was 4-5 times higher than that of newborn rats. In conclusion, newborn rats were 3-5 times more susceptible to 3EP and 4EP than young rats.
authors.affiliation: National Institute of Health Sciences, Kamiyoga, Tokyo, Japan.
authors.forename: Mika
authors.initials: M
authors.lastname: Takahashi
authors.forename: Mutsuko
authors.initials: M
authors.lastname: Hirata-Koizumi
authors.forename: Nobuo
authors.initials: N
authors.lastname: Nishimura
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Ito
authors.forename: Masao
authors.initials: M
authors.lastname: Sunaga
authors.forename: Sakiko
authors.initials: S
authors.lastname: Fujii
authors.forename: Eiichi
authors.initials: E
authors.lastname: Kamata
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Hasegawa
authors.forename: Makoto
authors.initials: M
authors.lastname: Ema
mesh_terms: D000284:Administration, Oral; D017677:Age Distribution; D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D008099:Liver / Q000187:drug effects* / Q000473:pathology; D008297:Male; D019055:No-Observed-Adverse-Effect Level; D010636:Phenols / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017678:Sex Distribution
chemical_list: D010636:Phenols; C497701:3-ethylphenol; C042291:4-ethylphenol