AIM:To explore the effects and mechanisms of 17β-estradiol on retinopathy of prematurity in rats.

METHODS: Eighty 7-day-old SD rats were randomly divided into normol group, high oxygen group, 17β-estradiol treatment group and vegetable oil treatment group. Rats of the high oxygen group were put into the environment exposed to 75% oxygen for 5d and backed to room air for another 5d to establish the oxygen-induced retinopathy model. The treatment group was given 17β-estradiol by injection with the dose of 0.5uL/rat/d(2μg/μL)before exposed to 75% oxygen. The vegetable oil treatment group is similar to 17β-estradiol treatment group but the medicine changed to vegetable oil. Counting the endotheliocyte nuclei of new vessels which extended from retina to vitreous body in the tissue-slice of HE staining, and investigate the change of retinal blood vessels by using methods of retina flat-mount. The expression of VEGF in retina by immunohistochemistry and reverse transcription-polymerase chain reaction(RT-PCR)analysis.

RESULTS: Rats treated with E₂ showed less neovascularization than high oxygen group and oxygen-exposed rats treated with vegetable oil(P<0.05). Adenosine diphosphate-ase(ADP ase)stained retina flat- mount showed that: less free-vascular areas and new blood vessels were seen in the 17β-estradiol treatment group compared with the high oxygen group. The expression of VEGF in 17β-estradiol treatment group lower than high oxygen group and vegetable oil treatment group, but higher than normal group in immunohistochemistry and RT-PCR analysis.

CONCLUSION:17β-estradiol has prevention effects in retinal neovascularization and the mechanism may involve in its interaction with VEGF.