The Protection Effect And The Mechanism Of Rock Tea Extract On Experimental Retinal Light Damage In Rats

Part IThe Establishment of Retinal Light Damage Model in Rats and the study on PathomorphologyObjective:To establish the model of retinal light damage in Sprague-Dawley rats and observe the changes of pathomorphology after retinal light injuryMethod:Sprague-Dawley (SD) rats were randomly divided into2groups:normal control group, light damage model group. After24hours in the dark environment, Light damage group was exposed to constant white fluorescent lamp irradiation for12hours at the average illuminance4000±200Lux. The retinal alteration was used for paraffin sections, HE staining which was observed the morphological changes.Result:1、The light injury modal in rat was successfully established.2、In normal control group, the morphology of retina was normal and the structure had a clear arrangement. The outer nuclear layer cells which were about10-12layer arranged neatly and the staining was even; The border between the inner and outer segment of the photoreceptor cells was clear. For the light damage model group, every layer of retinal structure was loose and the interlayer boundary was not clear. The INL cells arranged in loose disorder and the nuclear layer reduced while the thickness of ONL cells was significantly thinner, about3～4cell thickness. The ONL cells gap increased and some nucleus became pyknotic. We can see few vacuoles in the photoreceptor cells.3^After light expose, compared with normal group, the thickness of the ONL became thinner in the model group.(P<0.05);Conclusion:The pathological change of chronic light damage of retina in rats which was induced by constant irradiation for12hours at the average illuminance4000±200Lux is a cell’s degenerative process. The main damage is in the ONL cells and photoreceptor cells. Part IIThe Protective Effect of Rock Tea Extract on Retinal Light Damage in RatsObjective:To observe the pathological morphology and biochemistry index changes of the light-induced damage in rats by injecting rock tea extract to the tail vein of rats. We want to explore the protective effect and mechanism of rock tea extract on rat retinal light damage and to provide basis for clinical treatment.Method:Forty Sprague-Dawley rats were randomly divided into4groups:normal control group, light damage model group, high dose group and low dose group. The experimental group exposed to constant white fluorescent lamp irradiation for12hours at the average illuminance4000±200Lux after24hours in the dark environment. Rock tea extract was given every day by caudal vein3days before irradiation and7days after irradiation. All the rats were killed after irradiation. The left eye retina was used for the detection of SOD and MDA activity, the right one was used for paraffin sections, HE staining which was observed the morphological changes of retina.Result:1.. In the light damage model group, every layer of retinal structure was loose and the interlayer boundary was not clear. The INL cells arranged in loose disorder and the nuclear layer reduced while the thickness of ONL cells was significantly thinner, about3～4cell thickness. The ONL cells gap increased and some nucleus became pyknotic. We can see few vacuoles in the photoreceptor cells. The form of the high dose group was relatively intact, the ONL became slightly thinner and the arrangement of inner and outer segment of the photoreceptor cells was regular. But in the low dose group, the ONL cells arranged in disorder and became thinner. We can see few vacuoles in the inner and outer segment of the photoreceptor cells. 2、After7days of light expose, SOD activity is57.88±6.32U/mgprot and MDA content is3.99±0.59nmol/mgprot in the normal group. SOD activity in the model group reduced while MDA increased significantly (P<0.05). SOD in the treatment group increased and MDA reduced compared with model group (P<0.05). We can see obvious changes in high dose group than in low dose group ((P<0.05).3%After light expose, compared with normal group, the thickness of the ONL became thinner (P<0.05); the treatment group improved, and the high dose group was better than the low one(P<0.05).Conclusion:1、Rock tea extract has protective effect on morphology of retina in the light damage rats, and can helps to maintain the normal physiological function.2、Rock tea extract can enhance the activity of SOD in the tissue of rat retina while decrease the content of MDA obviously. It also can significantly reduce light damage to the retina caused by oxidative stress reaction. So it has the effect of anti-oxidation and maybe has a certain role of delaying the retinal light damage and protecting visual cells.3、The protective effect of rock tea extract on light damage retina is in dose dependence.