Experimental Study Of Nitric Oxide And Vascular Endothelial Growth Factor In Retinopathy Of Prematurity

Objective To observe the level of nitric oxide(NO) in retina of Retinopathy of Prematurity(ROP) model and discuss the influences on neovascularization and expression of vascular endothelial growth factor (VEGF) in retina of ROP model after the use of L-N6-(1-Iminoethyl)lysine(L-NIL) and N-Nitro-L-arginine(L-NNA).Methods 1) The ROP model of newborn Sprague-Dawley (SD) rats was induced by hyperxia. The rats were randomly divided into groups in air , groups in hyperxia, groups treated with L-NNA under hyperxia-exposure and the control groups under hyperxia-exposure, groups treated with L-NIL under hyperxia-exposure and the control groups under hyperxia-exposure, groups treated with L-NNA under relative hypoxia -exposure and the control groups under relative hypoxia–exposure. 2) The absorbance was determined to detect the activity of constructive nitric oxide syntheses (cNOS) and induced nitric oxide syntheses (iNOS) in retina of groups in air and groups in hyperxia, which reflected the level of NO in retina. 3) Drug treatment: groups treated with L-NNA under hyperxia-exposure and groups treated with L-NNA under relative hypoxia–exposure were respectively injected with L-NNA(150mg/kg·d that was 50ml/kg·d) through intraperitoneal route in hyperxia and relative hypoxia. The control groups under hyperxia-exposure and the control groups under relative hypoxia–exposure were respectively injected with saline(50ml/kg·d) through intraperitoneal route in hyperxia and relative hypoxia. Groups treated with L-NIL under hyperxia-exposure and the control groups under hyperxia-exposure were respectively injected with L-NIL(25mg/kg·d that was 10ml/kg·d) and saline(10ml/kg·d) through intraperitoneal route in hyperxia. 4) As soon as the relative hypoxia finished, eyeballs of newborn rats were enucleated for hematoxylin and eosin stain sections to count the nuclei of proliferative retinal vessels, and complete retinas were isolated to determine the expression of VEGF by Western Blot. Results The activity of cNOS in retina of groups in hyperxia(in hyperxia 0.1953±0.0244 U/mgprot,in relative hypoxia 0.1472±0.0149 U/mgprot) increased significantly as compared with groups in air(in hyperxia 0.1237±0.0380 U/mgprot,in relative hypoxia period 0.0959±0.0268 U/mgprot) (P<0.05), the activity of iNOS decreased significantly(P<0.05). Comparing with control group(control groups under hyperxia 135.18±22.99,control groups under relative hypoxia 135.15±23.36), the number of nuclei of proliferative retinal vessels in L-NNA treated group(groups treated with L-NNA under hyperxia 89.19±11.86,groups treated with L-NIL under relative hypoxia 79.62±10.87) decreased significantly(P<0.05) and the expression of VEGF in retina increased 60.38% in hyperxia but decreased 17.97% in relative hypoxia. There was no significant difference in above indexes between L-NIL treated group and control group(P>0.05).Conclusion Inhibition of cNOS can reduce NO induced activity of vascular and cytotoxicity so it can reduce the impairment of vascular endothelial cell. And inhibition of cNOS can also download the expression of VEGF in retina. All these lead to the depression of retinal neovascularization.