Stimulation of DNA synthesis and c-fos expression in corneal endothelium by insulin or insulin-like growth factor-I.
OBJECTIVE
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.


CONCLUSIONS
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.
Department of Ophthalmology, University of California, San Diego School of Medicine.
S T
ST
Feldman
D
D
Gately
B L
BL
Seely
A
A
Schonthal
J R
JR
Feramisco
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis*; D004261:DNA Replication; D004728:Endothelium, Corneal / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D011869:Radioligand Assay; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism
D007328:Insulin; D016760:Proto-Oncogene Proteins c-fos; D007334:Insulin-Like Growth Factor I; D004247:DNA; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin