Stimulatory effect of insulin-like growth factor I on proliferation of mouse pituitary cells in serum-free culture.
IGF-I is synthesized in the human and rat anterior pituitary glands. The present study was designed to clarify the growth-promoting action of IGF-I on mouse pituitary cells in a primary serum-free culture system. Proliferation of pituitary cells was detected by monitoring the cellular uptake of bromodeoxyuridine (BrdU). BrdU labelling in the nucleus was found in all types of secretory cells: corticotrophs, thyrotrophs, gonadotrophs (LH cells and FSH cells), somatotrophs and mammotrophs. IGF-I (75 ng/ml) stimulated the proliferation of corticotrophs and mammotrophs among the pituitary secretory cells. IGF-I receptor mRNA was detected in the cultured pituitary cells using reverse transcription (RT)-PCR, indicating that mouse pituitary cells expressed IGF-I receptors. Insulin (100 ng/ml) or IGF-I (7.5 ng/ml) failed to increase the percentage of BrdU-labelled cells. However, treatment with insulin (100 ng/ml) plus IGF-I (7.5 ng/ml) increased the percentage of BrdU-labelled cells in a synergistic-like manner. Genistein, a tyrosine kinase specific inhibitor, decreased the IGF-I-induced cell proliferation, indicating that IGF-I acts through IGF-I receptors. IGF-I mRNA was also detected in the cultured pituitary cells by RT-PCR, and its peptides were immunocytochemically detected. The present results demonstrate that all types of pituitary secretory cells have the ability to proliferate in our serum-free culture system. IGF-I synthesized in the pituitary gland may stimulate the growth of pituitary cells, in particular corticotrophs and mammotrophs, by an autocrine or paracrine mechanism.
Oomizu
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Department of Biology, Faculty of Science, Okayama University, Japan.
Takeuchi
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Takahashi
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D000818:Animals; D015139:Blotting, Southern; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D007150:Immunohistochemistry; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000235:genetics / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010902:Pituitary Gland / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010907:Pituitary Hormones / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000032:analysis; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D013268:Stimulation, Chemical
D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D007328:Insulin; D010907:Pituitary Hormones; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D017526:Receptor, IGF Type 1