A possible role of insulin-like growth factor-II C-peptide in regulating the function of steroidogenic cells in adult frog adrenal glands.
The sole structural determinant for the differential ability of the insulin-like growth factors (IGF-I and IGF-II) to induce autophosphorylation of specific insulin receptor (IR) tyrosine residues and activate downstream signaling molecules is the C domain. The IR is structurally related to the type I insulin-like growth factor receptor (IGF-IR). This study aimed to identify the presence of IGF receptors by which the IGF-II C-peptide could mediate its effects in the frog (Rana ridibunda) adrenal glands and to observe whether injection of IGF-II C-peptide affects the function of adrenal steroidogenic cells using light and transmission electron microscopy and by the evaluation of the immunoreactivity of steroidogenic acute regulatory protein (StAR). After IGF-II C-peptide injection, there was a reduction of StAR protein immunoreactivity levels, an accumulation of large lipid droplets in close contact with each other, and an induction of proliferation of the steroidogenic cells. These results indicate a possible role of IGF-II C-peptide in steroidogenic cell function and in induction of steroidogenesis. The detection in this study of IGF-I receptor (IGF-IR) immunoreactivity in frog adrenal glands also indicates that the metabolic and mitogenic effects of IGF-II C-peptide in these glands may occur via the IGF-IR.
Castillo
Songül Süren
SS
Istanbul University, Department of Biology, Faculty of Science, Zoology Section, 34459 Vezneciler, Istanbul, Turkey. songulsuren@yahoo.com
D000311:Adrenal Glands / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D007150:Immunohistochemistry; D007267:Injections; D007335:Insulin-Like Growth Factor II / Q000008:administration & dosage / Q000494:pharmacology*; D008027:Light; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology; D010750:Phosphoproteins / Q000493:pharmacokinetics / Q000494:pharmacology; D011895:Rana ridibunda; D000098682:Steroidogenic Acute Regulatory Protein
D010446:Peptide Fragments; D010750:Phosphoproteins; D000098682:Steroidogenic Acute Regulatory Protein; D007335:Insulin-Like Growth Factor II