252 Ontogeny of VEGF, IGF-I, and GH in the Rat Retina, Vitreous and Serum

Abstract

Background/Aim: Growth factors such as VEGF, IGF-I, and GH are implicated in retinal vascular development. Low serum IGF-I and high serum GH has been shown to be associated with ROP. The ocular compartments are protected by the blood-retinal barrier. We hypothesized that levels of growth factors in the ocular and systemic circulation are different and compartment-specific. We examine the ontogeny of VEGF, IGF-I and GH in rat retina, vitreous, and serum from birth (P0) to P21. Methods. Newborn rats (n=3 litters/group; 15 pups/litter) were sacrificed at P0, P7, P14 and P21. Retinal, vitreous and serum VEGF, IGF-I and GH levels were determined. Results: VEGF levels were 10-fold higher in the vitreous than serum at all stages of development. Vitreous and serum VEGF levels declined at P7, P14 and P21 (p<0.05 to p<0.001) compared to P0. In the retina, VEGF levels increased with highest concentrations at P21 (p<0.05 vs P0). IGF-I levels in the vitreous were comparable with serum levels and decreased from P7 through P21 (p<0.05) compared to P0. IGF-I levels in serum and retina increased with advancing postnatal age. Despite 4-fold higher IGF-I levels in the vitreous than retina at P0, equilibration was achieved at P21. GH levels in the vitreous were 10-fold lower than serum levels and were decreased at P14 and P21 (p<0.05 to p<0.001) compared to P0 and P7 in both compartments. GH levels in the retina remained unchanged from P0 through P21. Conclusions: The ontogenic patterns of vitreous VEGF and IGF-I during rat postnatal retinal development imply that the vitreous is a reservoir for these growth factors. VEGF, IGF-I and GH in the retina, vitreous and systemic circulation exhibit compartment-specific differences. These differences should be considered in conditions associated with retinal neovascularization, such as ROP.