| Introduction Retinopathy of prematurity ( ROP) was first reported in 1942 by Terry. During that time this kind of fibrous proliferation membrane was suggested to be the trace of congenital lens vessel membrane. Clinical observation believed it's not the truth. Nowadays, ROP is considered to relate closely with prematurity and low birth weight, in addition, the high concentration of oxygen supply after birth also played an important role. Meanwhile, Nitric oxide ( NO) and Nitric oxide synthesase(NOs) are regarded to take part in the process of pe-rioxidation of nerve and vessels, and also the ischemia and reperfusion damage. On the other hand, NO was believed to be one kind of endo-thelial relaxation factors, which could dilate the vessels. While how this two important factors changes in the ROP? We could hardly find any report now, so our study aimed to discuss the role of NO and NOs in the process of ROP.Materials and Methods272 eyes of one - day newborn wister rat were enrolled in our study. After being born, they were put into an oxygen supply box fed by their mothers. The concentration of oxygen was measured 3 times aday to keep at about 80%. Study group 1,2,3 and 4 included pups in-halating oxygen for 1,2,4 and 7 days respectively. Study group 5 ,6,7 and 8 included pups inhalating oxygen for continues 7 days, then living in air condition for 1,2,4 and 7 days respectively. Pups fed always in air condition after birth for 1,2,4,7,8,9,11 and 14 were served as control group(control group 1 -8 respectively). 8 eyes in each study group and 4 in control were used to detect the concentration of NO. Another 8 and 4 were to NOs. 10 eyes in study group 4 and its control , study group 8 and its control were observed the vessels of retina. Study group 5 ,6,7,8 and their control groups(4 eyes in each group) were detected their vessels newly generated.Results1. The concentration of oxygenoxygen concentration was 80.17 1. 885%2. vessels of the retinaIn the study group 4, after inhalating oxygen continuously for 7 days, the main vessels of retina thinnened obviously compared with its control group. There could be seen peripapillar capillaries of retina in the control group but no in the study group. One layer capillary on the retina formed in 7 - day newborn rats. In control group, this layer capillary had completely developed. ( pic. 3 ). While in study group the capillary on the peripheral of this layer seemed loose and many obvious leakage points could be found. From the overall view of retina, vessels of control retina developed more further to peripheral, nearly no leakage point could be seen. In study group 8 (inhalating oxygen for continuous 7 days, then living in air condition for 7 days) , maintrunk of retina vessels broadened obviously, peripapilla capillary developed well compared with study group 4, while compared with control group 8, this vessel still relatively thinnened, even one eye with very thin main trunk and poor developed capillaries. From the overall view, study retina appeared obviously poor compared with control. Meanwhile, no capillary could be seen on the peripheral area, under microscope, vessels presented obstructed and leakage, capillary developed poor in the study retina, while in control group, capillary developed well even at the peripheral area.3. Pathologic changes of retinaNewly generated capillaries were found in one eye of both study group 7 and 8.4. NO and NOs changes of retinaIn study group, NOs of retina expressed in a low level within 4 days of birth, rapidly increased in 7th day compared with control(P < 0. 01) , reached peak at 8th day, from then on kept at a high level although a little bit lower than that of 8th day. NO concentration presented the same trend as that of NOs, while in the control group, NOs kept at a lower level, although raising after 7th day, still obviously lowered than that of study group, with the peak level at the llth day, (P<0.05). NO kept at relatively lower level, its peak at 14th day (P<0.05).C...
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