IGF-I and EGF receptors in the pigmented rabbit bulbar conjunctiva.
The purpose of this study was to investigate whether receptors for insulin-like growth factors I and II (IGF-I and IGF-II), insulin, epidermal growth factor (EGF), and transforming growth factor alpha (TGF alpha) are present on the apical surface of the pigmented rabbit bulbar conjunctiva. Binding of 125I-labelled ligands to the apical surface of the pigmented rabbit bulbar conjunctiva was conducted at 4 degrees C in the absence and presence of excess unlabeled ligands. There was no evidence for the existence of IGF-II, insulin or TGF alpha receptors in the isolated pigmented bulbar conjunctiva. Only IGF-I and EGF receptors appeared to be present. The apparent dissociation constant (Kd) of IGF-I receptors was 206 +/- 13 pM and that for EGF was 51 +/- 5 pM. The number of receptors per 95 mm2 of bulbar conjunctiva was (6.0 +/- 0.2)X10(9) for IGF-I and (2.4 +/- 0.1)X10(9) for EGF. There was no crossover binding of either IGF-I or EGF to one another's receptors. The IC50 value for competitive displacement of bound 125I-IGF-I was: 44 +/- 2 nM by IGF-I, 156 +/- 13 nM by IGF-II and 812 +/- 78 nM by insulin. The IC50 value for displacement of bound 125I-EGF was 0.37 +/- 0.03 nM by EGF and 0.42 +/- 0.04 nM by TGF alpha. In conclusion, only IGF-I and EGF receptors appear to be present on the apical surface of the pigmented rabbit bulbar conjunctiva. The IGF-I receptor is also capable of binding IGF-II and insulin, whereas the EGF receptor is also capable of binding TGF alpha.
Narawane
M A
MA
Department of Pharmaceutical Sciences, University of Southern California, Los Angeles 90033, USA.
Lee
V H
VH
D000818:Animals; D003228:Conjunctiva / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D008024:Ligands; D009915:Orbit; D010858:Pigmentation; D011817:Rabbits; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D016211:Transforming Growth Factor alpha / Q000378:metabolism
D007328:Insulin; D008024:Ligands; D017527:Receptor, IGF Type 2; D016211:Transforming Growth Factor alpha; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D066246:ErbB Receptors; D017526:Receptor, IGF Type 1