Thyrotropin and triiodothyronine regulate iodothyronine 5'-deiodinase messenger ribonucleic acid levels in FRTL-5 rat thyroid cells.
We investigated the regulation of type I iodothyronine 5'-deiodinase (5'-D) gene expression by TSH and T3 in FRTL-5 rat thyroid cells. Northern blot analysis revealed that these cells express a 5'-D messenger RNA (mRNA) species of 2.1 kilobases. Readdition of TSH to FRTL-5 cells, precultured in both thyroid hormones and TSH-depleted medium for 4 days, increased 5'-D mRNA levels, reaching a maximum (2.8-fold compared to control) after 12 h of TSH (10 microU/ml) stimulation. Dibutyryl cAMP (DBC) and forskolin mimicked this stimulatory effect of TSH on 5'-D mRNA levels. T3 also increased the 5'-D mRNA levels, reaching a maximum (2-fold compared to control) after 8 h of T3 (10(-9) M) stimulation. Addition of TSH (10 microU/ml) or DBC (1 mM) together with T3 (10(-9) M) further increased 5'-D mRNA levels, reaching a maximum (5-fold compared to control) after 12 h of stimulation. Examination of the rate of disappearance of 5'-D mRNA levels after inhibition of mRNA transcription by actinomycin-D revealed that neither TSH nor T3 significantly affected the rate of disappearance. Cycloheximide, a protein synthesis inhibitor, almost completely blocked the induction of 5'-D mRNA by TSH and DBC, but did not block the induction by T3. These results suggest that both TSH and T3 increase 5'-D mRNA levels probably by increasing transcription rate, and that TSH regulates it, in part via the second messenger cAMP, for which cycloheximide-sensitive de novo protein synthesis is required, whereas T3 does without requiring it.
Toyoda
N
N
Second Department of Internal Medicine, Kansai Medical University, Osaka, Japan.
Nishikawa
M
M
Mori
Y
Y
Gondou
A
A
Ogawa
Y
Y
Yonemoto
T
T
Yoshimura
M
M
Masaki
H
H
Inada
M
M
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D007453:Iodide Peroxidase / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology*
D012333:RNA, Messenger; D014284:Triiodothyronine; D003609:Dactinomycin; D005576:Colforsin; D003994:Bucladesine; D013972:Thyrotropin; D003513:Cycloheximide; D007453:Iodide Peroxidase