Growth hormone regulation of growth hormone-releasing hormone gene expression.
Slot-blot hybridization technique was used to evaluate growth hormone-releasing hormone (GHRH) mRNA levels in the hypothalamus of long-term (14 days) hypophysectomized (HPX) rats treated or not with 125 micrograms hGH/rat, twice daily IP, since the first day postsurgery. In addition, mRNA levels were determined in the hypothalamus of short-term (4 days) GH-treated (250 micrograms hGH/rat, twice daily IP) intact rats. GHRH mRNA levels were increased in HPX rats, and GH treatment partially counteracted this rise. Short-term administration of GH decreased GHRH mRNA levels in intact rats. These results, evaluated together with previous findings showing decreased hypothalamic GHRH-like immunoreactivity in both HPX rats and intact rats given GH (6, 7, 9), indicate that GH exerts a negative feedback action on the synthesis and release of GHRH.
de Gennaro Colonna
V
V
Department of Pharmacology, School of Medicine, University of Milan, Italy.
Cattaneo
E
E
Cocchi
D
D
Müller
E E
EE
Maggi
A
A
D000818:Animals; D005786:Gene Expression Regulation / Q000187:drug effects; D005796:Genes / Q000187:drug effects; D013006:Growth Hormone / Q000494:pharmacology*; D013007:Growth Hormone-Releasing Hormone / Q000235:genetics*; D007016:Hypophysectomy; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012970:Sodium Glutamate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
D012333:RNA, Messenger; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D012970:Sodium Glutamate