Differential regulation of thyrotropin-releasing hormone receptor mRNA levels by thyroid hormone in vivo and in vitro (GH3 cells).
We studied the effect of thyroid status on thyrotropin-releasing hormone receptor (TRH-R) mRNA levels both in vivo and in vitro (GH3 cells) using a cloned rat TRH-R cDNA by RT-PCR. Experimental hypothyroid rats were produced by total thyroidectomy and were then killed 7 days after the operation. TRH receptor binding in the anterior pituitary and serum TSH level were elevated approximately 2-fold and 8-fold, respectively, in 7 day thyroidectomized rats. TRH-R mRNA levels in hypothyroid rats were also increased significantly compared with those of normal rats. In GH3 cells, however, no significant change of TRH-R mRNA level was observed between cultures treated with triiodothyronine (T3, 10(-9) and 10(-7) M) and the untreated group. The present data indicate that 1) the in vivo effects of thyroid status on TRH-R mRNA levels differ from the in vitro one, and that 2) the down regulation of TRH-R binding by thyroid hormone in GH3 cells may be mediated by translational or post-translational mechanisms.
Yamada
M
M
First Department of Internal Medicine, Gunma University School of Medicine, Japan.
Monden
T
T
Satoh
T
T
Iizuka
M
M
Murakami
M
M
Iriuchijima
T
T
Mori
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D003001:Cloning, Molecular; D015536:Down-Regulation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D007037:Hypothyroidism / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011061:Poly A / Q000235:genetics; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D018025:Receptors, Thyrotropin-Releasing Hormone; D013965:Thyroidectomy; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*; D014284:Triiodothyronine / Q000494:pharmacology*
D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D017981:Receptors, Neurotransmitter; D018025:Receptors, Thyrotropin-Releasing Hormone; D014284:Triiodothyronine; D011061:Poly A; D013973:Thyrotropin-Releasing Hormone; D012313:RNA