Distribution of epidermal growth factor (EGF) receptors in rabbit corneal epithelial cells, keratocytes and endothelial cells, and the changes induced by transforming growth factor-β1

Abstract

Three kinds of rabbit corneal cells (epithelial cells, keratocytes and endothelial cells) were cultured, and the growth promoting effects of epidermal growth factor (EGF) were examined in these cells. It was found that the sensitivity of the epithelial cells to EGF was the highest, that of the endothelial cells was a little lower, and that of the keratocytes was the lowest. Transforming growth factor-β1 (TGF-β1) did not influence growth of the three kinds of corneal cells. It was found that TGF-β1 enhanced the growth promoting effect of EGF in the keratocytes, but not in the epithelial and endothelial cells. EGF receptors in the corneal cells were labelled with [ 125I]EGF and analysed by Scatchard plot. In the epithelial and endothelial cells, both high and low affinity receptors were found, while the keratocytes had only low affinity receptor. In the epithelial cells, the number and the association constant of the high affinity receptors were, respectively, 2·79 × 10 4 per cell and 0·034 n m, and those of the low affinity receptors were, respectively, 13·4 × 10 4 per cell and 0·700 n m. In the endothelial cells, the number and the association constant of the high affinity receptors were 1·27 × 10 4 per cell and 0·086 n m, respectively, and those of the low affinity receptors were 8·91 × 10 4 per cell and 1·536 n m. In the keratocytes, the number of receptors and the association constant were 9·49 × 10 4 per cell and 1·535 n m, respectively. The corneal cells were treated with TGF-β1 for 24 hr and its influence on EGF receptors was examined. The results showed that TGF-β1 induced the high affinity receptors in the keratocytes, although TGF-β1 did not influence EGF receptors in the epithelial and endothelial cells. The number of high affinity receptors in keratocytes treated with TGF-β1 was 1·02 × 10 4 per cell and the association constant was 0·171 n m (this was approximately tenfold higher than that of the receptor of keratocytes not treated with TGF-β1).