Tri-iodothyronine increases insulin-like growth factor binding protein-4 expression in rat hepatocytes
| Autor: | Bottazzi C, Scharf Jg, Gabriella Gallo, Ilaria Demori, Adriana Voci, Emilia Fugassa |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 1997 |
| Předmět: |
Male
medicine.medical_specialty Transcription Genetic Endocrinology Diabetes and Metabolism medicine.medical_treatment Immunoblotting Insulin-like growth factor-binding protein Insulin-like growth factor Endocrinology In vivo Internal medicine Gene expression medicine Animals Northern blot RNA Messenger Rats Wistar Cells Cultured Triiodothyronine biology Dose-Response Relationship Drug Growth factor Peptide secretion Blotting Northern Rats Insulin-Like Growth Factor Binding Protein 1 Insulin-Like Growth Factor Binding Protein 2 Insulin-Like Growth Factor Binding Protein 4 Liver biology.protein Dactinomycin hormones hormone substitutes and hormone antagonists |
| Popis: | Previous in vivo studies demonstrated significant variations in insulin-like growth factor binding protein-1 (IGFBP-1), IGFBP-2 and IGFBP-4 hepatic mRNAs and/or serum levels depending on the rat thyroid status. In this study we employed cultured hepatocytes from adult rats to demonstrate a possible direct regulation of these genes by tri-iodothyronine (T3). Northern blot analysis revealed that IGFBP-1 and -4 messages were clearly expressed, whereas IGFBP-2 signal was barely detectable. No significant effects on IGFBP-1 mRNA level or on peptide secretion were detected in T3-cultured hepatocytes. In contrast, significant increases in IGFBP-4 mRNA steady-state levels as well as in IGFBP-4 secretion were observed in hepatocytes cultured for 12–24 h in the presence of T3. The T3 effect on IGFBP-4 transcript levels appears to consist of enhanced gene transcription and is independent of ongoing protein synthesis. The T3-increased IGFBP-4 expression in cultured hepatocytes is consistent with our in vivo experiments demonstrating an increase in hepatic IGFBP-4 mRNA and serum IGFBP-4 levels in T3-treated rats. Furthermore, significant decreases in hepatic IGFBP-4 message and serum IGFBP-4 levels were observed in hypothyroid rats compared with euthyroid controls. Our data establish an important direct role for thyroid hormone in regulating IGFBP-4 expression and consequently IGF activity. Journal of Endocrinology (1997) 154, 155–165 |
| Databáze: | OpenAIRE |
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