Comparative binding of bovine, human and rat insulin-like growth factors to membrane receptors and to antibodies against human insulin-like growth factor-1.
The immunological properties of human, bovine and rat insulin-like growth factors (IGF) and insulin were compared in competitive binding studies with Tr10 and NPA polyclonal antisera raised in rabbits against human IGF-1. Bovine IGF-1 was 11-19% as effective as human IGF-1 in competing for binding with 125I-labelled human IGF-1, whereas IGF-2 reacted poorly and insulin did not compete. Similar competitive binding curves were obtained with the mouse monoclonal anti-(human IGF-1) antibody 3D1, except that bovine IGF-1 showed a severalfold greater affinity for the monoclonal antibody than for either polyclonal antiserum. Membranes isolated from human placenta, sheep placenta and foetal-human liver were used as sources of cellular receptors. In human placental membranes, most of the binding of IGF-1 tracers could be attributed to a type-1 receptor, because insulin inhibited up to 65% of tracer binding. The other two tissues apparently contain only type-2 receptors, as evidenced by the very low potency of bovine or human IGF-1 in competing for binding with IGF-2 tracers and the absence of any competition by insulin. In competition for binding with labelled bovine or human IGF-1 to human placental membranes, bovine IGF-1 had a similar potency to human IGF-1, whereas bovine IGF-1 was more potent in binding studies with tissues rich in type-2 receptors. Rat IGF-2 was considerably less effective than human IGF-2 in competition for receptors on any of the membrane preparations.
D000818:Animals; D000906:Antibodies / Q000378:metabolism*; D001667:Binding, Competitive; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000276:immunology*; D007335:Insulin-Like Growth Factor II; D008099:Liver / Q000378:metabolism; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D011863:Radioimmunoassay; D051381:Rats; D011971:Receptors, Immunologic / Q000378:metabolism*; D013002:Somatomedins / Q000276:immunology* / Q000378:metabolism*; D013045:Species Specificity
D000906:Antibodies; D007328:Insulin; D011971:Receptors, Immunologic; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II