Reproductive Toxicity Of Cadmium And Protective Effects Of N-acetylcysteine On Sinopotamon Henanense

To explore reproductive toxicity of cadmium(Cd)and effects of N-acetylcysteine(NAC)on alleviation of cadmium-induced oxidative stress in the freshwater crab Sinopotamon henanense.We examined the acute and chronic effects of Cd.Acute effects were studied by treating crabs for 3,5 and 7 days with two Cd concentrations(7.25 or 14.5 mg/L)and chronic Cd treatment was achieved by treating crabs for 7,14 and 28 days,respectively,with 0.725 or 1.45 mg/L of Cd.There are three contents in our study:First Part.Effects of Cd on the ovaries of the freshwater crab S.henanense.We investigated the tissue accumulation of Cd,the activities of superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GPx),the contents of malonyldialdehyde(MDA)in lipid peroxidation,and the expression level of metallothionein MT.The results showed that Cd levels were significantly increased,in both dose-and time-dependent manners in the chronic groups and in a dose-dependent manner in the acute groups.In the chronic groups,the activities of antioxidant enzymes,SOD,CAT and GPx,initially decreased at day 7 or14,and increased after 14 and/or 28 days,which was accompanied by an increase of MDA and MT levels.In the acute groups,there were no statistically significant changes in the activities of the antioxidant enzymes nor in the levels of MDA and MT.Secend Part.Effects of Cd on the male accessory gland of S.henanense.We investigated the tissue accumulation of Cd,the effects of Cd on the microstructure and ultrastructure,the activities of SOD,CAT and GPx,the contents of MDA,protein carbonyl(PCO)and DNA-protein crosslinks(DPC)in the male accessory gland.The results showed that the tissue accumulation of Cd after treatment was significantly higher than the control group.With the increase of time and Cd concentration,the accumulation of Cd increased gradually,and the epithelial cells wereseparated from basement membrane even ruptured causing nucleus lost.Notably in the two Cd concentration groups on 28 d,the structure of basement membrane changed seriously,larger cavity appeared between epithelial cells and basement membrane,nucleus were lost seriously in epithelial cells.Using TEM technique,we found that,after the Cd treatment,the chromatin were condensed,the nuclear membrane were disappeared,the cristae of mitochondria were broken and showed vacuolization,rough endoplasmic reticulum and Golgi body were swelled in irregular shape,and the number of myeloid body increased.The activities of SOD and GPx increased at the early-stage and then decreased;while the activities of CAT increased as the concentration of Cd increased;The PCO contents,and DPC increased significantly in a time-and concentration-dependent manner.The contents of MDA increased at 7 d and 14 d,but decreased at 28 d.Third Part.Effects of NAC on the oxidative damages of the ovaries of S.henanense induced by Cd.We investigated the tissue accumulation of Cd,the activities of SOD,CAT and GPx,the contents of MDA and the changes in the microstructure in the ovarian tissues to study the effect of NAC on alleviation of cadmium-induced oxidative stress.The results showed that under the action of cadmium alone,with increasing Cd concentration,the accumulation of Cd and the contents of MDA were significantly increased compared with the control group.The activities of SOD,CAT and GPx increased at different time points.The micro-structure of ovarian was damaged in different levels.For the group of Cd combined with NAC in three different levels of concentration,the content of Cd in ovarian tissue decreased significantly on the 14 th and the28 th days,respectively.The activity of SOD decreased significantly on the 14 th day.The activities of CAT,GPx and the contents of MDA had a significant decrease on the 28 th day,and returned to normal levels gradually.With the extension of time and the increase of NAC's concentration,the damage of ovarian tissues became alleviated.That is,nuclear membranes were gradually repaired and there were only a small quantity of chromatin agglutinate.The vacuolation in cells and nuclei almost disappeared,with the structure of ovarian cells returning to normal conditions.The conclusions are as follow:Firstly,both acute and chronic cadmium exposure led to the accumulation of Cd in ovarian of S.henanense,but only chronic caused oxidative damage in the ovaries of S.henanense.Secondly,chronic cadmium treatment caused oxidative damage on the male accessory gland of S.henanense,especially on the epithelial layer of arterial walls,and produced oxidative damages to the oxidation system.It is speculated that the normal reproductive function of crabs may be affected.Thirdly,as an important antioxidant,NAC can effectively alleviated the oxidative damage of cadmium on ovary of S.henanense.It further proved that oxidative damage is an important mechanism of Cd toxicity on crabs.It also showed that NAC could protect aquatic animals from the cadmium pollution.