To address the question of insulin-like growth factor (IGF) I localization and synthesis in kidney, we used two complementary experimental approaches: immunohistochemistry of fixed paraffin-embedded rat kidney sections; and measurement of IGF I mRNA in isolated components of the rat nephron, using a highly sensitive and specific solution hybridization assay. Immunostainable IGF I was localized exclusively to principal cells of cortical and medullary collecting ducts. Administration of growth hormone to hypophysectomized rats for 8 d resulted in enhanced immunohistochemical staining of IGF I within collecting ducts, but no detectable IGF I in other portions of the nephron. The abundance of IGF I mRNA was 7-12-fold higher in isolated papillary collecting ducts than in proximal tubules or glomeruli, and was enriched 10-fold compared with whole kidney. Our data demonstrate colocalization of IGF I and IGF I mRNA in the collecting duct, consistent with focal expression of the IGF I gene at this site.
Focal expression of insulin-like growth factor I in rat kidney collecting duct.
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J D Bortz, P Rotwein, D DeVol, P J Bechtel, V A Hansen, M R Hammerman; Focal expression of insulin-like growth factor I in rat kidney collecting duct.. J Cell Biol 1 August 1988; 107 (2): 811–819. doi: https://doi.org/10.1083/jcb.107.2.811
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