The effect of hypophysectomy on pancreatic islet hormone and insulin-like growth factor I content and mRNA expression in rat
| Autor: | Caroline Maake, Jürgen Zapf, Elisabeth Eppler, Manfred Reinecke, Tanja Jevdjovic, Gunthild Krey, Cornelia Zwimpfer |
|---|---|
| Přispěvatelé: | University of Zurich, Reinecke, M |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Blood Glucose
Male medicine.medical_specialty endocrine system Histology 10017 Institute of Anatomy medicine.medical_treatment Radioimmunoassay Gene Expression 610 Medicine & health Biology Glucagon 2722 Histology 1307 Cell Biology Islets of Langerhans Insulin-like growth factor Internal medicine medicine 1312 Molecular Biology Animals Insulin RNA Messenger Insulin-Like Growth Factor I Rats Wistar Pancreas Molecular Biology In Situ Hybridization Pancreatic hormone Hypophysectomy Delta cell Body Weight 3607 Medical Laboratory Technology Organ Size Cell Biology Blotting Northern Pancreatic Hormones Immunohistochemistry Rats Medical Laboratory Technology medicine.anatomical_structure Endocrinology Somatostatin 570 Life sciences biology Hormone |
| Popis: | The growth arrest after hypophysectomy in rats is mainly due to growth hormone (GH) deficiency because replacement of GH or insulin-like growth factor (IGF) I, the mediator of GH action, leads to resumption of growth despite the lack of other pituitary hormones. Hypophysectomized (hypox) rats have, therefore, often been used to study metabolic consequences of GH deficiency and its effects on tissues concerned with growth. The present study was undertaken to assess the effects of hypophysectomy on the serum and pancreatic levels of the three major islet hormones insulin, glucagon, and somatostatin, as well as on IGF-I. Immunohistochemistry (IHC), in situ hybridization (ISH), radioimmunoassays (RIA), and Northern blot analysis were used to localize and quantify the hormones in the pancreas at the peptide and mRNA levels. IHC showed slightly decreased insulin levels in the beta cells of hypox compared with normal, age-matched rats whereas glucagon in alpha cells and somatostatin in delta cells showed increase. IGF-I, which localized to alpha cells, showed decrease. ISH detected a slightly higher expression of insulin mRNA and markedly stronger signals for glucagon and somatostatin mRNA in the islets of hypox rats. Serum glucose concentrations did not differ between the two groups although serum insulin and C-peptide were lower and serum glucagon was higher in the hypox animals. These changes were accompanied by a more than tenfold drop in serum IGF-I. The pancreatic insulin content per gram of tissue was not significantly different in hypox and normal rats. Pancreatic glucagon and somatostatin per gram of tissue were higher in the hypox animals. The pancreatic IGF-I content of hypox rats was significantly reduced. Northern blot analysis gave a 2.6-, 4.5-, and 2.2-fold increase in pancreatic insulin, glucagon, and somatostatin mRNA levels, respectively, in hypox rats, and a 2.3-fold decrease in IGF-I mRNA levels. Our results show that the fall of serum IGF-I after hypophysectomy is accompanied by a decrease in pancreatic IGF-I peptide and mRNA but by partly discordant changes in the serum concentrations of insulin and glucagon and the islet peptide and/or mRNA content of the three major islet hormones. It appears that GH deficiency resulting in a "low IGF-I state" affects translational efficiency of these hormones as well as their secretory responses. The maintenance of normoglycemia in the presence of reduced insulin and elevated glucagon serum levels, both of which would be expected to raise blood glucose, may result mainly from the enhanced insulin sensitivity, possibly due to GH deficiency and the subsequent decrease in IGF-I production. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|