Binding of insulin-like growth factor-I by glomerular endothelial and epithelial cells: further evidence for IGF-I action in the renal glomerulus.
The renal glomerulus is both a site of action and synthesis of IGF-I. We previously demonstrated the presence of IGF-I receptor and synthesis in glomerular mesangial cells. In this study we investigated the presence of specific IGF-I receptors on mouse glomerular endothelial and epithelial cells in culture. [125I]IGF-I specifically bound to the cell surface of both cell types. Maximum specific binding, 0.141 B/F for endothelial cells and 0.301 B/F for epithelial cells, was obtained at 22 degrees C after 150 min incubation. The estimated Kd values were 2.25 x 10(-9) for endothelial cells and 1.5 x 10(-9) for epithelial cells. Cross-linking studies showed a single band of radioactivity with an estimated mol wt of 145K, consistent with the alpha-subunit of the IGF-I receptor. Radiolabelled IGF-I was not degraded by either cell types. These findings suggest a possible paracrine action of IGF-I in the renal glomerulus.
Conti
F G
FG
Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Elliot
S J
SJ
Striker
L J
LJ
Striker
G E
GE
D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive; D002850:Chromatography, Gel; D003432:Cross-Linking Reagents; D004727:Endothelium / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007678:Kidney Glomerulus / Q000378:metabolism*; D051379:Mice; D011956:Receptors, Cell Surface / Q000378:metabolism; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*
D003432:Cross-Linking Reagents; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I