Stimulation of DNA synthesis and c-fos expression in corneal endothelium by insulin or insulin-like growth factor-I.
PURPOSE. To study the growth regulation of bovine corneal endothelium, the effects of insulin and insulin-like growth factor-I on the expression of the c-fos proto-oncogene as well as on DNA synthesis were analyzed. Bovine corneal endothelial cells were also analyzed for the presence of insulin and insulin-like growth factor-I receptors. METHODS. Indirect immunofluorescence was used to assess the effect of stimulation by insulin and insulin-like growth factor-I on c-fos protein expression and DNA synthesis quiescent bovine corneal endothelium. Receptor number was determined by 125I-insulin or 125I-IGF-I binding studies. RESULTS. Fetal bovine serum strongly stimulated c-fos protein expression and DNA synthesis. Insulin-like growth factor-I was less effective while insulin was effective only at high concentrations. Scatchard analysis of 125I-insulin-like growth factor-I and 125I-insulin binding to bovine corneal endothelium revealed 180,000 IGF-I receptors and 7,000 insulin receptors. CONCLUSION. The number of insulin-like growth factor-I receptors far exceeds the number of insulin receptors in bovine corneal endothelium, suggesting that the effects of insulin on c-fos gene expression and mitogenesis were likely to be mediated through the insulin-like growth factor-I receptor.[1]References
- Stimulation of DNA synthesis and c-fos expression in corneal endothelium by insulin or insulin-like growth factor-I. Feldman, S.T., Gately, D., Seely, B.L., Schonthal, A., Feramisco, J.R. Invest. Ophthalmol. Vis. Sci. (1993) [Pubmed]
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