IGF-I and EGF receptors in the pigmented rabbit bulbar conjunctiva

Abstract

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.

Characterization of epithelial primary cultures from human conjunctiva

“…It can be inferred that EGF could also exert important effects upon conjunctival epithelial cells. Recently, the presence of receptors for EGF in the surface of rabbit bulbar conjunctiva has been demonstrated [23]. Fixed sections of conjunctiva have reacted positively against EGF-R MoAb in the epithelium in both humans [3,21] and monkeys [3].…”

Insulin secretion by rat lachrymal glands: effects of systemic and local variables

“…Previous data have identified insulin in the tear film of rabbits and humans (26,31). Our study provides information about the presence of insulin in the tear film and LG of normal rats, as indicated by immunohistochemistry, with a mechanism of secretion possibly based on secretory granules.…”

“…glucose transportertear filmocular surface THE TEAR FILM CARRIES IMMUNOGLOBULIN, lysozyme, and lactoferrin involved in ocular surface defence, growth factors responsible for cell proliferation and differentiation, and hormones, including insulin, that provide signals for various types of information to peripheral tissues (19,26,32,41).…”