Effects of thyroxine, triiodothyronine and reverse triiodothyronine on the neonatal hypothyroid rat cerebellum.
In order to develop a model of thyroid hormone action, we studied the effect of small doses of T3 and T4 on the development of the hypothyroid neonatal cerebellum of rat pubs. Using granulosa cell death at postnatal d15 (picnotic index) as a criterion of hypothyroidism, it was found that a single injection of 50 ng T3/10g bw or 180 ng T4/10 g bw would reduce the picnotic index to levels found in euthyroid rat cerebelli. We further tested if rT3, known to be an excellent blocker of deiodinase type 2 activity, would be able to block the effects of T4. 20 micrograms rT3/10g bw had to be given to be an effective inhibitor in vivo. This dose did not affect the potency of T4 and control experiments with rT3 alone indicated that rT3 was capable of reducing the picnotic index to euthyroid levels. It is speculated that rT3 might act at the nuclear receptor but also at the cell membrane.
Dubuis
J M
JM
Department of Medicine, University Hospital of Geneva, Switzerland.
Sanchez-Menegay
C
C
Burger
A G
AG
D000818:Animals; D002531:Cerebellum / Q000196:embryology* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005865:Gestational Age; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000196:embryology*; D007231:Infant, Newborn; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000502:physiology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology; D011247:Pregnancy; D051381:Rats; D013974:Thyroxine / Q000097:blood / Q000494:pharmacology*; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology*; D014285:Triiodothyronine, Reverse / Q000097:blood / Q000494:pharmacology*
D007527:Isoenzymes; D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D007453:Iodide Peroxidase; D013974:Thyroxine