title: The relationship between basal and regulated Gnrhr expression in rodent pituitary gonadotrophs.
abstract: Hypothalamic GnRH together with gonadal steroids and activins/inhibin regulate its receptor gene (Gnrhr) expression in vivo, which leads to crucial changes in GnRHR numbers on the plasma membrane. This is accompanied by alterations in the gonadotroph sensitivity and responsiveness during physiologically relevant situations. Here we investigated basal and GnRH-regulated Gnrhr expression in rodent pituitary gonadotrophs in vitro. In pituitary cells from adult animals cultured in the absence of GnRH and steroid hormones, the Gnrhr expression was progressively reduced but not completely abolished. The basal Gnrhr expression was also operative in LβT2 immortalized gonadotrophs never exposed to GnRH. In both cell types, basal transcription was sufficient for the expression of functional GnRHRs. Continuous application of GnRH transiently elevated the Gnrhr expression in cultured pituitary cells followed by a sustained fall without affecting basal transcription. Both basal and regulated Gnrhr transcriptions were dependent on the protein kinase C signaling pathway. The GnRH-regulated Gnrhr expression was not operative in embryonal pituitary and LβT2 cells and was established neonatally, the sex-specific response patterns were formed at the juvenile-peripubertal stage and there was a strong correlation between basal and regulated gene expression during development. Thus, the age-dependent basal and regulated Gnrhr transcription could account for the initial blockade and subsequent activation of the reproductive system during development.
authors: Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892-4510, United States.
authors: Ivana
authors: I
authors: Bjelobaba
authors: Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892-4510, United States.
authors: Marija M
authors: MM
authors: Janjic
authors: Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892-4510, United States.
authors: Jovana S
authors: JS
authors: Tavcar
authors: Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892-4510, United States.
authors: Marek
authors: M
authors: Kucka
authors: Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892-4510, United States.
authors: Melanija
authors: M
authors: Tomić
authors: Section on Cellular Signaling, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892-4510, United States. Electronic address: stojilks@mail.nih.gov.
authors: Stanko S
authors: SS
authors: Stojilkovic
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002461:Cell Line, Transformed; D000242:Cyclic AMP / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D052681:Gonadotrophs / Q000187:drug effects / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D011493:Protein Kinase C / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D011966:Receptors, LHRH / Q000235:genetics* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D011966:Receptors, LHRH; D000242:Cyclic AMP; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium
keywords: ERK1/2; GnRH; Gnrhr; Gonadotrophs; LβT2 cells; Protein kinase C