Characterization of type II insulin-like growth factor (IGF) receptors in sheep liver plasma membranes.
Interactions of insulin-like growth factors (IGFs) from recombinant human and natural ovine sources with sheep liver plasma membranes have been studied. Total specific binding of 125I-hIGF-II (40%) to liver plasma membranes greatly exceeded that of 125I-hIGF-I (1.5%) after incubation at 20 C for 90 min. Binding of 125I-hIGF-II to the plasma membranes was dependent upon time, temperature and membrane concentration of the incubation. Binding of 125I-hIGF-II was only partially reversed by addition of 100 nM IGF-II (18%) or by dilution with excess buffer (36%). Competitive inhibition studies of 125I-hIGF-II binding demonstrated that IGF-II from ovine or recombinant human sources was more effective at inhibiting binding than ovine or human IGF-I. Insulin did not affect binding of 125I-hIGF-II. Plasma membranes were affinity cross-linked to 125I-IGF-II followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis in the presence and absence of the reducing agent dithiothreitol. Following autoradiography, radioactive bands were localized at 274,000 Mr and 210,000-215,000 Mr in the presence and absence of reducing agent, respectively. This pattern was unaffected by 100 nM human or ovine IGF-I or 1,000 nM insulin, but coincubation with 100 nM human or ovine IGF-II eliminated the radioactive band. These data indicate that an IGF-II specific receptor is present in sheep liver plasma membranes which has characteristics similar to those of nonruminant Type II receptors.
Hossner
K L
KL
Department of Animal Sciences, Colorado State University, Fort Collins 80523.
Yemm
R S
RS
D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017451:Receptors, Somatomedin; D012756:Sheep / Q000378:metabolism*; D013002:Somatomedins / Q000378:metabolism*; D013045:Species Specificity
D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II