Assessment of developmental effects of hypothyroidism in rats from in utero and lactation exposure to anti-thyroid agents.
To clarify the developmental effects of hypothyroidism and to establish a detection system of resultant brain retardation, pregnant rats were administered 3 or 12 ppm of 6-propyl-2-thiouracil (PTU) or 200 ppm of methimazole (MMI) in the drinking water from gestation day 10 to postnatal day 20 and maintained after weaning until 11 weeks of age (adult stage). Offspring displayed evidence of growth retardation lasting into the adult stage, which was particularly prominent in males. Except for hypothyroidism-related thyroid follicular cell hypertrophy, most histopathological changes that appeared at the end of chemical exposure were related to growth retardation and reversed by the adult stage. A delayed onset of puberty and an adult stage gonadal enlargement occurred by exposure to anti-thyroid agents, both being especially evident in males, and this effect might be related to gonadal growth suppression during exposure. At the adult stage, the distribution variability of hippocampal CA1 pyramidal neurons reflecting mismigration could be detected in animals receiving both thyrotoxins, with a dose-dependent effect by PTU. Similarly, a reduction in the area of the corpus callosum and oligodendroglial cell numbers in the cerebral deep cortex, both reflecting impaired oligodendroglial development, were detected in rats administered both chemicals. Thus, all effects, except for impaired brain development, might be linked to systemic growth retardation, and the brain morphometric methods employed in this study may be useful to evaluate the potency of chemicals to induce hypothyroidism-related brain retardation.
Shibutani
Makoto
M
Division of Pathology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan. mshibuta@cc.tuat.ac.jp
Woo
Gye-Hyeong
GH
Fujimoto
Hitoshi
H
Saegusa
Yukie
Y
Takahashi
Miwa
M
Inoue
Kaoru
K
Hirose
Masao
M
Nishikawa
Akiyoshi
A
D000818:Animals; D000831:Animals, Newborn; D013956:Antithyroid Agents / Q000633:toxicity*; D001835:Body Weight / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D004195:Disease Models, Animal; D004622:Embryo, Mammalian / Q000187:drug effects* / Q000196:embryology; D005260:Female; D005317:Fetal Growth Retardation / Q000139:chemically induced / Q000503:physiopathology; D005835:Genitalia / Q000187:drug effects / Q000473:pathology; D007037:Hypothyroidism / Q000097:blood / Q000139:chemically induced* / Q000503:physiopathology; D008297:Male; D009836:Oligodendroglia / Q000187:drug effects / Q000378:metabolism; D009929:Organ Size / Q000187:drug effects; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011441:Propylthiouracil / Q000633:toxicity*; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051381:Rats; D013961:Thyroid Gland / Q000187:drug effects / Q000254:growth & development; D013963:Thyroid Hormones / Q000097:blood
D013956:Antithyroid Agents; D013963:Thyroid Hormones; D011441:Propylthiouracil