St. Feldman et al., STIMULATION OF DNA-SYNTHESIS AND C-FOS EXPRESSION IN CORNEAL ENDOTHELIUM BY INSULIN OR INSULIN-LIKE GROWTH FACTOR-I, Investigative ophthalmology & visual science, 34(6), 1993, pp. 2105-2111
Purpose. To study the growth regulation of bovine corneal endothelium,
the effects of insulin and insulin-like growth factor-I on the expres
sion of the c-fos proto-oncogene as well as on DNA synthesis were anal
yzed. Bovine corneal endothelial cells were also analyzed for the pres
ence of insulin and insulin-like growth factor-I receptors. Methods. I
ndirect immunofluorescence was used to assess the effect of stimulatio
n by insulin and insulin-like growth factor-I on c-fos protein express
ion and DNA synthesis quiescent bovine corneal endothelium. Receptor n
umber was determined by I-125-insulin or I-125-IGF-I binding studies.
Results. Fetal bovine serum strongly stimulated c-fos protein expressi
on and DNA synthesis. Insulin-like growth factor-I was less effective
while insulin was effective only at high concentrations. Scatchard ana
lysis of I-125-insulin-like growth factor-I and I-125-insulin binding
to bovine corneal endothelium revealed 180,000 IGF-I receptors and 7,0
00 insulin receptors. Conclusions. The number of insulin-like growth f
actor-I receptors far exceeds the number of insulin receptors in bovin
e corneal endothelium, suggesting that the effects of insulin on c-fos
gene expression and mitogenesis were likely to be mediated through th
e insulin-like growth factor-I receptor.