Regulation of the growth hormone (GH) receptor and GH-binding protein mRNA.
In fasting rats, a transient increase in growth hormone-binding protein (GHBP) mRNA levels was observed after 1 day, in muscle, heart, and liver, but not in fat tissues. The liver GH receptor (GHR) mRNA level was significantly increased after 1 day (but not after 5 days) of bovine GH (bGH) treatment in fed rats. Both the liver GHR mRNA level and the net increment of plasma IGF-I markedly decreased after 5 days of bGH administration in fasting rats. These findings suggest that GHR and GHBP mRNAs in the liver are expressed in a different way and that the expression of GHBP mRNA is regulated differently between tissues, at least in rats. The results also suggest that refractoriness to GH in a sustained fasting state might be beneficial in preventing anabolic effects of GH. In humans, GHR mRNA in lymphocytes, from subjects with either GH-deficiency or acromegaly, could be detected by the reverse transcription-polymerase chain reaction method. In one patient with partial GH insensitivity, a heterozygous missense mutation (P561T) was identified in the cytoplasmic domain of GHR.
Department of Medicine, Kobe University School of Medicine, Japan.
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Kaji
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Ohashi
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Abe
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Chihara
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D018076:DNA, Complementary / Q000737:chemistry; D005215:Fasting; D005786:Gene Expression Regulation / Q000187:drug effects; D013006:Growth Hormone / Q000494:pharmacology; D006801:Humans; D008099:Liver / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011986:Receptors, Somatotropin / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014018:Tissue Distribution
D002352:Carrier Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D013006:Growth Hormone; C051815:somatotropin-binding protein