Growth hormone regulates growth hormone receptor gene transcription in primary human thyroid cells.
In this study the regulation of GH-receptor gene (GHR/GHBP) transcription by different concentrations of GH (0, 12.5, 25, 50, 150, 500 ng/ml) with and without variable TSH concentrations (0.5, 2, 20 mU/l) in primary human thyroid cells cultured in serum-free hormonally-defined medium was studied. The incubation time was 6 h and GHR/GHBP mRNA expression was quantitatively assessed by using PCR amplification at hourly intervals. Correlating with the GH-concentrations added a constant and significant increase of GHR/GHBP gene transcription was found. After the addition of 12.5 ng/ml GH, GHR/GHBP mRNA concentration remained constant over the incubation period of 6 h but in comparison with the experiments where no GH was added there was a significant change of GHR/GHBP mRNA expression. Following the addition of 25 ng/ml GH a slight but further increase of GHR/GHBP transcription products was seen which increased even more in the experiments where higher GH concentrations were used. These data focusing on GHR/GHBP gene transcription derived from cDNA synthesis and quantitative PCR amplification were confirmed by run-on experiments. Furthermore, cycloheximide did not affect these changes supporting the notion that GH stimulates GHR/GHBP gene transcription directly. In a second set of experiments, in combination with variable TSH levels, identical GH concentrations were used and no difference in either GHR/GHBP mRNA levels or in transcription rate (run-on experiments) could be found. In conclusion, we report data showing that primary thyroid cells express functional GH-receptors in which GH has a direct and dose dependent effect on the GHR/GHBP gene transcription. Furthermore, TSH does not a have a major impact on GHR/GHBP gene regulation.
Mullis
P E
PE
Department of Paediatrics, Division of Paediatric Endocrinology, University Children's Hospital, Inselspital, CH-3010, Bern, Switzerland. primus.mullis@insel.ch
O'Donovan
N
N
Eblé
A
A
Marti
U
U
Diem
P
P
Bürgi
U
U
Peter
H J
HJ
D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D019382:Human Growth Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011986:Receptors, Somatotropin / Q000235:genetics*; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism*; D013972:Thyrotropin / Q000008:administration & dosage; D014158:Transcription, Genetic / Q000187:drug effects
D002352:Carrier Proteins; D017931:DNA Primers; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D019382:Human Growth Hormone; D013972:Thyrotropin; C051815:somatotropin-binding protein