The Experimental Research Of The Expression Change And Mechanism Of Aquaporin-1 In Lens Epithelial Cells Of Streptozotocin-induced Rat

Objective To investigate the expression change of aquaporin-1 ( AQP1 ) in the membrane of lens epithelial cells (LECs) and the relation between this change and the expression of Calpain-2 in the cytoplasm of lens LECs and the total Ca2+ level in lenses of rat diabetic cataract( DC ).Methods An animal model of diabetes was induced by a single intravenous dose of streptozotocin (STZ, 60mg/kg body weight) in 2-month-old male Wistar rats. The transparency of all lens were examined under microscope and photographied every week. The eyeballs of both sides were extracted periodically from each experimental groups and control group. The eyeballs of one side were made into paraffin sections. The histological changes were examined under light microscope. Immunohistochemical techniques and computer-imaging analysis were used to localize and semi-quantify the expression of AQP1 and Calpain-2 in LECs. The lenses of other side were isolated and the concentration of Ca2+ was determined by a SpectrAA–40 atomic absorption spectrophotometer.Results All lenses in control group remained transparency and all lenses in experiment groups developed cataract of different stages. The breakage of the lens structure was gradually aggravated from stage I to stage IV. The expression of AQP1 on the cell membrane decreased significantly before the DC occurred and decreased gradually with the diabetes development. The elevated level of Calpain-2 in the cytoplasm of LECs and the increased ion concentration of Ca2+ in lenses were observed before lens opacification began. The expression of Calpain-2 increased gradually with the diabetes development and the concentration of Ca2+ did so.Conclusion Decreased expression of Aquaporin-1 in the membrane of LECs of rat diabetic cataract were closely correlated with elevated expression of Calpain-2 in the cytoplasm of LECs and increased ion concentration of Ca2+ in lens.