title: Is GHRH receptor essential to GHRP-2-induced GH secretion in primary cultured rat pituitary cells?
abstract: It is still controversial in rat whether the stimulation of GH secretion by GH-releasing peptides (GHRP) requires both GHRP receptor (GHRP-R) and GH-releasing hormone receptor (GHRH-R). To clarify this issue, we have postulated that inhibition of GHS-R or GHRH-R gene transcription should block GHRP-2-induced GH secretion. Rat pituitary cells were incubated for 3 days in the presence or absence of antisense 18-mer phosphorothiate oligonucleotides (ONs) complementary to the codon region of GHS-R or GHRH-R mRNAs. A significant decrease in GHRH-R and GHS-R mRNA levels was found in corresponding antisense-treated cells compared with the control cells treated with sense ON. Treatment with antisense GHS-R ON reduced (but not abolished) GHRP-2-induced GH secretion although GHRH-induced GH secretion was not altered. GHRH-stimulated GH secretion was totally abolished by the treatment with antisense GHRH-R ON, whereas GHRP-2 induced GH secretion was not affected. Treatment of cells with both GHS-R and GHRH-2 ONs however completely inhibited GHRH and GHRP-2-stimulated GH secretion. These results suggest that GHRH-R is vital for GHRH-induced GH secretion but only partially involved in GHRP-2-stimulated GH secretion under the condition of down-regulation of GHS-R gene transcription.
authors.affiliation: Lab of Animal Molecular Physiology, Faculty of Agriculture, Shinshu University, Naganoken 399-4598, Japan.
authors.forename: Sang-Gun
authors.initials: SG
authors.lastname: Roh
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.forename: Ki-Choon
authors.initials: KC
authors.lastname: Choi
authors.forename: Yogendra
authors.initials: Y
authors.lastname: Shrestha
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Sasaki
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism; D008297:Male; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D018013:Receptors, Neuropeptide / Q000378:metabolism / Q000502:physiology*; D018017:Receptors, Pituitary Hormone-Regulating Hormone / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D016376:Oligonucleotides, Antisense; D009842:Oligopeptides; D012333:RNA, Messenger; D018013:Receptors, Neuropeptide; D018017:Receptors, Pituitary Hormone-Regulating Hormone; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; C091874:growth hormone-releasing peptide-2; C048250:somatotropin releasing hormone receptor