Experimental Study On The Effects Of Seawater On Function And Morphology In The Retina Of Rabbits

Objective:To observe the changes of function and morphology in the retina of rabbits that seawater was injected into the vitreous and explore the possible mechanism in it.Then evaluate the state of injury and supply experimental basis for clinical treatment.Methods:48 New-Zealand white rabbits were selected and eyes were checked.The weight is 2.5kg to 3.0kg.Then 40 rabbits were selected randomly to make the animal models.3mm penetrating wound that run parallel with superotemporal Corneal limbus 5mm was made in every right eyeball sclera with.paracentesis knife,then cut off the vitreous of outflow,1ml artificial seawater was injected into the intermedius of rabbits vitreous.The wound was sewed up with 6-0 nylon sutures.Then lml balanced salt solution(BSS) was injected into the vitreous of left eyeball in the same way as control group.The rabbits were randomly divided into 5 groups on the basis of 30 minutes,2 hours,6 hours,12 hours,24 hours after the injury.At different times.after the wounding,the eyeballs were enucleated respectively after examination with dark adaptation F-ERG to observe the pathological changes under the light,microscope, explore the ultramicroscopic structure alteration under the electron microscope,and then the TUNEL method was used to detect the retinal cell apoptosis,the immunohistochemical method was used to observe the expression of Bcl-2 and Bax proteinum.8 rabbits exposed to none factor were defined as normal group.All the original data was dealed and analyzed with statistical method.Results:(1)There had no statistical difference on b-wave amplitude of F-ERG between BSS control groups and normal group.The b-wave amplitude gradually decrease after the injury in seawater groups,and the.difference was significant after 6 hours contrast to the control groups.There had no significant difference between 12h and 24h in the seawater groups.(2)The pathological changes of the retina:The BSS control groups had no obvious pathological changes in the retina compared with the normal group at the different times.Observed by light microscope,the structures of retina begin to appear an alteration in seawater groups at 2 hours,the cytoplasm showed vesiculation and swelling in the photoreceptor cell,the inner nuclear layer cell and the ganglion cell at 6 hours.At 12 hours,the structures of bacillary layer changed obviously,the row of the outer nuclear layer cell was irregular,the inner nuclear layer cell showed vesiculation and swelling obviously and the cell population was decreased in the ganglion cells and the inner nuclear layer cells.Through the transmission electron microscope,we observed the mitochondrias showed vesiculation and swelling,the mitochondrial crista was broken in the segment of rod at 6 hours in seawater groups.At 12 hours,the chromatin became pycnotic obviously in the inner nuclear layer cells.We also observed karyorrhexis at this time in this layer.The ganglion cells' nuclear membranes were cavate and the chromatin was enriched.(3)The immunohistochemistry and cell apoptosis:TUNEL positive cells were few in BSS control groups and normal groups.In.seawater groups,there were a few positive cells at 30 minutes,the number of positive cells were increased at 6 hours,and there had statistical difference compared with control group.The total number of the apoptotic cells achieved its peak.The expression of Bcl-2 protein increased at 30 minutes and 2 hours,and decreased from 6 hours in seawater groups. The expression of Bax proteinum gradually increased at the different times in seawater groups,there had significant difference after 6 hours,the expression had no obvious changes in BSS control group,,and had no statistical difference compared with normal group.The ratio of Bcl-2/Bax gradually decreased followed the time in seawater groups.Conclusions:(1)The retina function was damaged after 6 hours with seawater was injected into the vitreous body of rabbits' eyeball,and the damage was aggravated following the time.(2)The morphology of the retina was changed after 2 hours with seawater was injected into the vitreous body of rabbits' eyeball,and the changes appeared obvious at 6 hours when checked by light microscope.Between 12 and 24 hours the damage became unrecoverable,the number was decreased in the ganglion cells and the inner nuclear layer cells.The chromatin was enriched and became pycnotic at 12 hours when checked by transmission electron microscope. (3)Apoptosis exists in the retina after seawater was injected in the vitreous body of rabbits' eyeball.Bcl-2 and Bax play an important role in the mechanism of retinal cells apoptosis.The decrease of retinal cells is closely relative to the ratio of Bcl-2/Bax.