Demonstration of type I insulin-like growth factor receptors on human platelets.
Human platelets, freshly isolated from healthy human adults, express receptors for insulin-like growth factor I. The IC50 for displacement of 125I-IGF-I binding by unlabeled IGF-I was 0.2 nM, by IGF-II 32 nM by insulin 160 nM. Scatchard analysis of IGF-I binding demonstrates dissociation constants of 0.14 +/- 0.08 nM for high affinity binding site and 54 +/- 18 nM for low affinity binding site. The presence of the alpha-subunit of type I IGF receptor, as high affinity binding site, was verified by affinity crosslinking of 125I-IGF-I to platelet surface membranes. Under reducing con-conditions a Mr = 135,000 band was preferentially labeled. The complete type I IGF receptor complex, which revealed under nonreducing conditions, has an approximately molecular mass of Mr greater than 400,000. The immunoprecipitation of the 125I-IGF-I cross-linked type I receptor with alpha IR-3 confirmed the results achieved by affinity crosslinking.
Hartmann
K
K
Department of Pediatrics, University of Heidelberg, FRG.
Baier
T G
TG
Loibl
R
R
Schmitt
A
A
Schönberg
D
D
D000328:Adult; D001792:Blood Platelets / Q000032:analysis*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008970:Molecular Weight; D011233:Precipitin Tests; D011956:Receptors, Cell Surface / Q000032:analysis* / Q000276:immunology; D017451:Receptors, Somatomedin
D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D007334:Insulin-Like Growth Factor I