Characterization of insulin-like growth factor receptors in human thyroid tissue.
We have characterized the binding of 125I-IGF-I and 125I-IGF-II to plasma membranes purified from human thyroid tissue. IGF binding was time- and temperature-dependent. At 4 degrees C, maximal specific binding of 125I-IGF-I was 17.3 +/- 2.5% and of 125I-IGF-II was 8.8 +/- 2.0% (mean +/- SD/60 micrograms membrane protein). 125I-IGF-I binding was inhibited completely by unlabeled IGF-I, IGF-II, insulin, and the type-I IGF receptor monoclonal antibody, alpha IR-3. 125I-IGF-II was inhibited completely by unlabeled IGF-II and nearly completely by IGF-I. 125I-IGF-II binding also was inhibited significantly by insulin, suggesting that much or all of the IGF-II was bound to the type-I IGF receptor. Scatchard analysis revealed a single class of binding sites with a Kd of 6.0 +/- 4.2 x 10(-10) M for IGF-I binding and 5.7 +/- 1.3 x 10(-10) M for IGF-II binding. IGF-I binding was inhibited by a variety of salts in a dose-dependent manner, calcium and magnesium salts being more effective than sodium or potassium salts. Affinity crosslinking of 125I-IGF-I and -II showed clear evidence only for type-I IGF receptors. Thus, a crude plasma membrane fraction of human thyroid tissue expresses predominantly type-I IGF receptors.
Cissewski
K
K
Charles A. Dana Research Laboratories, Department of Medicine, Beth Israel Hospital, Boston, MA.
Wolf
M
M
Moses
A C
AC
D000345:Affinity Labels; D002462:Cell Membrane / Q000378:metabolism; D003432:Cross-Linking Reagents; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D017527:Receptor, IGF Type 2 / Q000378:metabolism*; D013388:Succinimides; D013961:Thyroid Gland / Q000378:metabolism*
D000345:Affinity Labels; D003432:Cross-Linking Reagents; D017527:Receptor, IGF Type 2; D013388:Succinimides; D017526:Receptor, IGF Type 1; C019358:disuccinimidyl suberate