Gonadotropins induce accumulation of insulin-like growth factor I mRNA in pig granulosa cells in vitro.
Pig granulosa cells have been shown to synthesize insulin-like growth factor (IGF) I peptide in vitro, and this expression is regulated by gonadotropins via the cAMP pathway. By hybridizing an IGF I cDNA probe with total RNA isolated from pig granulosa cells cultured in vitro, we show that these cells contain two IGF I transcripts of about 0.9 kb and 9 kb in size. Treatment of the cells with gonadotropins (follicle-stimulating hormone, luteinizing hormone) or cAMP agonists (dibutyryl-cAMP, forskolin) induces an accumulation of the transcripts which can be abolished by transcriptional inhibitors, but not by translational inhibitors. We thus provide new evidence that pig granulosa cells are a site of IGF I synthesis, and we conclude that (1) gonadotropins increase IGF I mRNA levels; (2) the accumulation of IGF I mRNA results from an increased transcription; (3) the stimulation of IGF I gene transcription does not require ongoing protein synthesis; (4) these effects of follicle-stimulating hormone can be mimicked by cAMP agonists.
Hatey
F
F
Laboratoire de Génétique Cellulaire, Institut National de la Recherche Agronomique, Castanet-Tolosan, France.
Langlois
I
I
Mulsant
P
P
Bonnet
A
A
Benne
F
F
Gasser
F
F
D000818:Animals; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D005260:Female; D006062:Gonadotropins / Q000502:physiology*; D006107:Granulosa Cells / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism*; D013552:Swine; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology
D006062:Gonadotropins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D003609:Dactinomycin; D007334:Insulin-Like Growth Factor I