铅镉联合暴露对大鼠肾脏功能损伤的研究

目的 探讨铅、镉对大鼠肾脏功能损伤的联合毒性作用.方法 对大鼠进行铅(300 mgPb/L)、镉(50 mgCd/L)单独和联合(300 mgPb/L 50 mgCA/L)饮水染毒8周.检测尿液中碱性磷酸酶(UALP)、N-乙酰-β-D-氨基葡萄糖苷酶(UNAG)、γ-谷氨酰基转移酶(UGGT)活力和总蛋白(utp)、α-微球蛋白(Ua<,1>-MG)、微量白蛋白(UmAlb)含量的动态变化.结果 单独染毒除2周时Pb、Cd组Ua<,1>-MG含量与Pb组UALP活力外,其余所测指标均从染毒2周开始明显高于对照组(P＜0.05;P＜0.01),且升高幅度与染毒时间呈正相关;联合染毒组从2周开始,所测指标均明显高于对照组(P＜0.01).在整个试验过程中,联合染毒组尿酶活力和尿蛋白含量均高于单独染毒组.结论 Pb、Cd联合暴露对大鼠肾脏功能的损伤呈协同毒性效应.     

三氯乙酸染毒对肝L-02细胞的增殖作用及对DNA甲基化水平的影响

目的 检测三氯乙烯(TCE)主要代谢产物三氯乙酸(TCA)对人肝L-02细胞染毒24 h后的增殖作用,以及对DNA总体甲基化水平的影响,探索TCE对肝L-02细胞的表型遗传毒性.方法 选择0.1-0.9 mmol/L浓度TCA作为合适的染毒剂量对肝L-02细胞染毒24 h后分别进行下列试验:以CCK-8试剂盒观测细胞的生长曲线;以抗5-mC抗体进行免疫荧光检测细胞核中胞嘧啶甲基化总体水平(代A 0.9 mmol/L染毒24 h);以流式细胞仪(FCM)检测其对细胞周期的影响及凋亡情况;提取细胞DNA进行琼脂糖电泳分析其对DNA的损伤作用.以上试验必要时设置5-氮杂胞苷(5-aza-dC5 μmol/L)处理的L-02细胞为基因组DNA低甲基化的对照以及肝癌细胞作为细胞周期分析的对照.结果 TCE在0.1～0.9 mmol/L浓度下染毒24 h后可以促进肝L-02细胞生长,并在0.9 mmol/L浓度作用下24 h可致肝L-02细胞DNA总体甲基化水平降低,荧光强度和正常细胞比较明显减弱;细胞周期分析发现TCA处理24 h后再用正常培养基继续培养24 h后可使细胞S G2期中细胞比例增加(与肝癌细胞接近);DNA梯状电泳分析未发现DNA损伤性改变.结论 TCA染毒24 h可促进细胞生长,可诱导基因组DNA低甲基化,并造成细胞周期的改变.提示TCA对肝细胞的早期细胞毒性作用与表型遗传机制有关.     

低铅负荷对淋巴细胞膜电位影响的分析

目的:探讨不同剂量铅对淋巴细胞增殖及细胞膜电位的影响,进一步明确低铅染毒淋巴细胞膜参数表达机制。方法:将小鼠脾淋巴细胞悬液分为四组,分别为10-6mmol/L Pb Cl2染毒组、10-5mmol/L Pb Cl2染毒组、10-4mmol/L Pb Cl2染毒组,磷酸盐缓冲盐水(PBS)作为对照组;在培养不同时间段(0 h,24 h,48 h,72 h)的细胞悬液中加入不等量的单克隆抗体,同时用细胞感受性色素di BA-C4标记淋巴细胞,测定细胞膜电位,从而确定细胞膜受体表达的情况以及淋巴细胞增殖情况的变化。结果:随Pb2+染毒浓度增高及时间延长,Pb2+染毒淋巴细胞di Bh-C4荧光强度明显增加,膜内的电位出现不同程度的升高,细胞膜受体表达呈阳性变化。10-6mmol/L Pb Cl2染毒组与淋巴细胞的增殖指数比较,差异无统计学意义(P>0.05),10-5mmol/L Pb Cl2染毒组、10-4mmol/L Pb Cl2染毒组染毒72 h,淋巴细胞增殖指数与对照组比较,差异有统计学意义(P<0.05)。结论:Pb Cl2染毒对淋巴细胞膜电位表达具有时间依赖性和饱和性;浓度>10-6mmol/L Pb Cl2染毒淋巴细胞具有抑制淋巴细胞增殖的作用。     

氯沙坦对慢性肾脏疾病患者血浆中炎症性细胞因子及TGF-β1的影响

目的研究血管紧张素Ⅱ受体拮抗剂-氯沙坦对慢性肾脏疾病患者血浆细胞因子浓度及尿转化生长因子β1排泄的影响,探讨其保护肾脏的可能机制。方法选取符合入选标准的慢性肾脏疾病患者32例,观察6个月,ELISA法检测血浆TNF-α、IL-6及尿TGF-β1的水平;免疫散射比浊法检测血浆hs CRP;放射免疫法检测尿白蛋白的浓度;全自动生化分析仪测定治疗前后血尿素氮、肌酐、HDL-C、LDL-C。结果与氯沙坦治疗前基础值相比,患者血浆hs CRP水平[(1 403±198)ng/m L vs.(998.1±138)ng/m L]明显增高(P<0.05),尿白蛋白/尿肌酐[(73.4±16.5)mg/mmol.Cr vs.(96.5±12.1)mg/mmol.Cr)]和TGF-β1/尿肌酐[(43.56±17.49)mg/mmol.Cr vs.(78.81±40.32)mg/mmol.Cr]水平明显降低,差异有统计学意义(P<0.05);TNF-α[(1.39±0.03)pg/m L vs.(1.46±0.04)pg/m L]、IL-6[(1.79±0.07)pg/m L vs.(1.81±0.09)pg/m L]水平变化差异无统计学意义(P>0.05)。与治疗前基础值比较,LDL-C[(117.0±1.4)mg/d L vs.(126.0±2.7)mg/d L]显著降低,但BUN[(28.3±0.6)mg/d L vs.(21.1±0.8)mg/d L]明显升高,差异有统计学意义(P<0.05);血肌酐[(139.4±36.3)μmol/L vs.(124.5±52.5)μmol/L]、HDL-C[(58.6±0.9)mg/d L vs.(56.2±3.0)mg/d L]与治疗前比较,差异无统计学意义(P>0.05)。结论氯沙坦对慢性肾脏疾病患者的肾脏有保护作用,其部分机制可能与上调细胞因子hs CRP和下调TGF-β1作用有关。     

辛硫磷对大鼠生殖内分泌系统的影响

目的 研究辛硫磷对雄性大鼠生殖内分泌系统的影响.方法 将每日不同剂量辛硫磷(5.9、29.4、147.0) mg/kg分别对雄性成年SD大鼠连续灌胃染毒15 d和30 d,应用RIA法测定血清卵泡刺激素(FSH)、黄体生成素(LH)、睾酮(T)和睾丸匀浆中睾酮(T)的水平,同步测定睾丸标志酶酸性磷酸酶(ACP)、γ-谷氨酰转移酶(γ-GT)的活性,并采用精子头计数法观测每日精子生成量(Spr)的变化.结果 与对照组比较,染毒大鼠15 d时,血清LH水平5.9 mg/kg,各染毒组表现为显著升高(P<0.05);血清FSH的水平随染毒剂量增加而升高,各染毒组均明显高于对照组(P<0.01);血清T水平随染毒剂量的增加呈现为升高的趋势,在147.0 mg/kg剂量组差异有统计学意义(P<0.05).染毒至30 d时,血清中LH水平在147.0 mg/kg剂量组差异有统计学意义(P<0.05);FSH在≤29.4 mg/kg剂量组表现有统计学意义(P<0.05).ACP各染毒组有统计学意义(P<0.01).γ-GT的活性在≥29.4 mg/kg剂量组范围均有明显差异(P<0.01).Spr与染毒剂量有明显的剂量依赖关系,在≥29.4 mg/kg剂量范围Spr显著减少(P<0.01).结论 辛硫磷对雄性大鼠有明显的生殖毒性,可影响其血清及睾丸性激素水平和酶活性,导致精子生成障碍.     

枸杞汁对DEHP致大鼠氧化损伤和血脂异常保护作用研究

目的探讨枸杞汁对邻苯二甲酸二乙基己基酯(DEHP)染毒所致氧化损伤和血脂异常的干预作用及差异。方法将实验大鼠分为对照组、DEHP组(1 500 mg/kg)、GSH干预组(500 mg/kg GSH+1 500 mg/kg DEHP)和枸杞汁干预组(枸杞原汁+1 500 mg/kg DEHP),连续灌胃7 d,测定大鼠血清及肝中谷胱甘肽过氧化物酶(GSH-Px)、超氧化物歧化酶(SOD)的活性以及血脂水平。结果与对照组相比,DEHP染毒会导致血清中GSH-Px活性、甘油三酯(TG)、高密度脂蛋白(HDL-C)浓度降低,差异有统计学意义(P0.05或P0.01),TG/HDL-C和非高密度脂蛋白胆固醇(non-HDL-C)浓度升高,差异有统计学意义(P0.05或P0.01),肝中GSH-Px、SOD活性差异有统计学意义(P0.05或P0.01);与DEHP组比较,枸杞汁和GSH均能使血清中GSH-Px活性升高,TG/HDL-C降低(P0.05或P0.01),枸杞汁组non-HDL-C、GSH组LDL-C浓度降低(P0.05),2个干预组大鼠肝中SOD活性均低于DEHP组,上述差异均有统计学意义。结论 DEHP染毒会导致大鼠肝氧化损伤及血脂水平异常,枸杞汁与GSH的作用相似,即对DEHP诱导的氧化损伤和血脂异常具有良好的调节保护作用。     

砷联合MC染毒致小鼠肝损伤的效应研究

目的观察砷(As)和微囊藻毒素(MC)单独及联合染毒对小鼠血清及肝组织肝功能指标和氧化损伤指标的影响。方法 40只健康KM小鼠随机分为4组,分别为对照组、染砷组(12.5μg/L)、染MC组(0.25μg/kg·dl)和联合染毒剂量组(12.5μg/L+0.25μg/kg·dl)。腹腔注射染毒10周,测定血清和肝组织中ALT、AST、MDA、SOD和GSH-Px水平。结果各染毒组血清白蛋白和ALT的水平与对照组比较差异均无统计学意义(P0.05);与对照组比较,各染毒组的AST水平均升高,其中染MC组和联合染毒组差异有统计学意义(P0.05);与对照组相比,染砷组和联合染毒组SOD和GSH-Px活性均增高,差异有统计学意义(P0.05)。MDA变化不明显。与对照组比较,肝组织中的白蛋白降低,变化有统计学意义(P0.05);与对照组比较染MC组和联合染毒组的ALT、AST水平均有升高,且差异有统计学意义(P0.05),各组间MDA含量差异无统计学意义(P0.05),各组间SOD活性呈下降趋势,但差异无统计学意义(P0.05);GSH-Px活性在各染毒组均显著增高,有统计学意义(P0.05)。肝组织DNA在染砷及染MC组时有损伤,联合染毒时损伤更明显。结论低剂量MC-LR及砷和MC联合染毒可以诱导小鼠肝功能损伤和DNA损伤,但抗氧化酶在染毒组增高,可对抗其氧化损伤作用。     

大鼠急性光气吸入对机体氧化损伤的研究

目的研究光气急性吸入对机体氧化损伤及抗氧化损伤状态的影响。方法将20只SD大鼠随机分成对照组和染毒组,利用三光气在N,N-二甲基甲酰胺作用下分解生成光气的方法,对染毒组动物进行动态恒量染毒,分别测定丙二醛(MDA)含量、总抗氧化力、还原型谷胱甘肽(GSH)、氧化型谷胱甘肽(GSSG)和总蛋白含量。结果染毒组实验动物血清和肝组织MDA含量较对照组均显著升高[(5.57±0.28)和(5.86±0.17)μmol/L,P<0.05;(455.55±74.81)和(516.97±42.74)nmol/g、pr,P<0.05)],染毒组动物血清和肝组织的总抗氧化力也显著升高[(7.10±1.36)和(9.67±3.02)U/ml,P<0.05,(2.70±0.40)和(3.13±0.26)U/mg,P<0.01)]。但GSH和GSSG在血清和肝组织中变化却有所不同,在血清中,染毒组动物GSH含量显著低于对照组(P<0.01),GSSG含量显著高于对照组(P<0.01);但在肝脏中,染毒组动物GSH含量较对照组升高显著(P<0.01),GSSG含量反而显著降低(P<0.05)。结论光气急性吸入可以引起全身ROS水平的显著升高,造成肺脏组织以外的其他组织脏器的氧化损伤,这为光气损伤机制的深入研究和光气中毒救治以及并发症的防治提供了一条新思路。     

硝酸钐染毒对雄性小鼠性行为的影响

目的 探讨不同剂量硝酸钐给药后对雄性小鼠性行为的影响.方法 ICR品系雄性小鼠随机分设5组,自由饮用含硝酸钐0,5,50,500,2000mg/L的溶液90d,运用动物行为学方法观察小鼠各性行为指标的变化.结果 硝酸钐染毒后,雄性小鼠爬跨潜伏期随着染毒剂量的增加而延长,呈现直线变化的剂量对数-效应关系,y:134.5904 34.9810lgx(r=0.9521,P<0.05).其中高剂量(2000mg/L)组小鼠爬跨潜伏期、射精潜伏期和射精间隔期与对照组相比明显延长(P<0.01;P<0.05;P<0.01),而爬跨次数与射精次数明显减少(P<0.01;P<0.05).结论 硝酸钐染毒会对雄性小鼠性行为产生影响.在本实验染毒剂量与研究条件下,亚慢性硝酸钐染毒90d的生殖毒性阈剂量是50mg/L.     

砷联合MC染毒致小鼠肝损伤的效应研究北大核心CSCD

目的观察砷(As)和微囊藻毒素(MC)单独及联合染毒对小鼠血清及肝组织肝功能指标和氧化损伤指标的影响。方法 40只健康KM小鼠随机分为4组,分别为对照组、染砷组(12.5μg/L)、染MC组(0.25μg/kg·dl)和联合染毒剂量组(12.5μg/L+0.25μg/kg·dl)。腹腔注射染毒10周,测定血清和肝组织中ALT、AST、MDA、SOD和GSH-Px水平。结果各染毒组血清白蛋白和ALT的水平与对照组比较差异均无统计学意义(P>0.05);与对照组比较,各染毒组的AST水平均升高,其中染MC组和联合染毒组差异有统计学意义(P<0.05);与对照组相比,染砷组和联合染毒组SOD和GSH-Px活性均增高,差异有统计学意义(P<0.05)。MDA变化不明显。与对照组比较,肝组织中的白蛋白降低,变化有统计学意义(P>0.05);与对照组比较染MC组和联合染毒组的ALT、AST水平均有升高,且差异有统计学意义(P<0.05),各组间MDA含量差异无统计学意义(P>0.05),各组间SOD活性呈下降趋势,但差异无统计学意义(P>0.05);GSH-Px活性在各染毒组均显著增高,有统计学意义(P<0.05)。肝组织DNA在染砷及染MC组时有损伤,联合染毒时损伤更明显。结论低剂量MC-LR及砷和MC联合染毒可以诱导小鼠肝功能损伤和DNA损伤,但抗氧化酶在染毒组增高,可对抗其氧化损伤作用。     

Accumulation and toxicity of aluminium-contaminated food in the freshwater crayfish, Pacifastacus leniusculus

The accumulation and toxicity of aluminium in freshwater organisms have primarily been examined following aqueous exposure. This study investigated the uptake, excretion and toxicity of aluminium when presented as aluminium-contaminated food. Adult Pacifastacus leniusculus were fed control (3 μg aluminium/g) or aluminium-spiked pellets (420 μg aluminium/g) over 28 days. Half the crayfish in each group were then killed and the remainder fed control pellets for a further 10 days (clearance period). Concentrations of aluminium plus the essential metals calcium, copper, potassium and sodium were measured in the gill, hepatopancreas, flexor muscle, antennal gland (kidney) and haemolymph. Histopathological analysis of tissue damage and sub-cellular distribution of aluminium were examined in the hepatopancreas. Haemocyte number and protein concentration in the haemolymph were analysed as indicators of toxicity. The hepatopancreas of aluminium-fed crayfish contained significantly more aluminium than controls on days 28 and 38, and this amount was positively correlated with the amount ingested. More than 50% of the aluminium in the hepatopancreas of aluminium-fed crayfish was located in sub-cellular fractions thought to be involved in metal detoxification. Aluminium concentrations were also high in the antennal glands of aluminium-fed crayfish suggesting that some of the aluminium lost from the hepatopancreas is excreted. Aluminium exposure via contaminated food caused inflammation in the hepatopancreas but did not affect the number of circulating haemocytes, haemolymph ion concentrations or protein levels. In conclusion, crayfish accumulate, store and excrete aluminium from contaminated food with only localised toxicity.     

Gill EROD in monitoring of CYP1A inducers in fish: a study in rainbow trout (Oncorhynchus mykiss) caged in Stockholm and Uppsala waters

The gill filament 7-ethoxyresorufin O-deethylase (EROD) assay was evaluated as a monitoring tool for waterborne cytochrome P4501A (CYP1A) inducers using rainbow trout (Oncorhynchus mykiss) caged in urban area waters in Sweden. To compare the CYP1A induction response in different tissues, EROD activity was also analyzed in liver and kidney microsomes. Immunohistochemistry was used to localize CYP1A protein in gill and kidney. In two separate experiments fish were caged at sites with fairly high expected polyaromatic hydrocarbon (PAH) contamination. In the first experiment, gill EROD activities were analyzed in fish exposed for 1-21 days in a river running through Uppsala. The reference site was upstream of Uppsala. In the second, gill, liver and kidney EROD activities were analyzed in fish exposed for 1-5 days in fresh or brackish waters of Stockholm and in a reference lake 60km north of Stockholm. Fish exposed for 5 days followed by 2 days of recovery in tap water in the laboratory were also examined. The gill consistently showed a higher EROD induction compared with the liver and the kidney. After 1 day of caging, gill EROD activity was markedly induced (6-17-fold) at all sites examined. Induction in gill was pronounced (5-7-fold) also in fish caged at the reference sites. In the 21-day exposure study gill EROD activity remained highly induced throughout the experiment (26-fold at most) and the induced CYP1A protein was exclusively confined to the gill secondary lamellae. In the 5-day exposure experiment, EROD activity peaked after 1 day and then declined in both gill and liver, while CYP1A immunostaining in the gill remained intense over the 5-day period. In the kidney, CYP1A staining was weak or absent. We conclude that gill EROD activity is a more sensitive biomarker of exposure to waterborne CYP1A inducers than EROD activity in liver and kidney.     

Tissue-specific cadmium and metallothionein levels in freshwater crab Sinopotamon henanense during acute exposure to waterborne cadmium

The freshwater crabs Sinopotamon henanense were exposed to different concentrations of waterborne cadmium (Cd). The relationship between tissue-specific Cd accumulation and metallothionein (MT) induction was investigated using the Cd saturation assay and atomic absorption spectrophotometry method. The results showed that Cd accumulation rose significantly in all tissues studied after Cd exposure, and the Cd accumulation level in various tissues followed the following order: gill > hepatopancreas > muscle > ovary. MT levels were clearly tissue-specific after Cd exposure. Hepatopancreas was found to have the highest MT level, followed by the gill, muscle, and ovary. In conclusion, the results indicated although Cd exposure clearly resulted in MT induction, its synthesis does not correlate with Cd accumulation in the later stage of Cd exposure. The calculated ratios of actual Cd to theoretical maximum Cd-MT in the hepatopancreas were <1.0 under acute waterborne Cd at all sampling points, indicating that the hepatopancreas had much greater Cd-binding potential of MT than the gill, muscle, or ovary. It is clear from our results that a positive correlation was shown between MT induction and Cd accumulation both in hepatopancreas and gill. Therefore, MT induction can be considered as a biomarker for acute waterborne Cd pollution.     

Comparison of the subacute effects of cadmium exposure upon nucleic acid, cyclic adenosine 3',5'-monophosphate and polyamine metabolism in lung and kidney cortex.

The timecourse of the cadmium-inflicted changes in DNA, polyamines, and cyclic AMP has been investigated in lung and renal cortex tissue of rats. In pulmonary tissue, heavy metal administration (2 × 1.0 mg/kg/day) produced an initial depression in the incorporation of [¹⁴C]-thymidine into DNA after 3 days, followed by a subsequent, significant enhancement at 5 days with maximal augmentation occurring after 7 days of cadmium treatment. In contrast the incorporation of labeled thymidine into kidney cortex DNA was decreased at all time periods studied and statistically significant reduction to at least half of the control values was noted at 3, 5 and 7 days. No apparent differences were found between pulmonary and renal DNA concentrations which were decreased at 1 day and elevated after 7 days of cadmium exposure in both tissues. Whereas cadmium significantly lowered lung RNA concentrations after 1, 3, or 5 days, heavy metal treatment failed to produce any significant change in RNA content of the kidney cortex. In general, subacute exposure to cadmium resulted in a significant rise in pulmonary putrescine, spermidine, and spermine after 3 and 5 days, although a significant depression was observed at 7 days in the case of putrescine. Surprisingly, the renal concentrations of putrescine and spermine were elevated in metal-treated animals but there was a statistically significant reduction in spermidine content. As in the case of incorporation of [¹⁴C]-thymidine into DNA, pulmonary cyclic AMP concentrations were depressed initially at 1 day and continuation of cadmium treatment for 3, 5, or 7 days resulted in enhancement of cyclic nucleotide concentration. In contrast, administration of the heavy metal lowered both the incorporation of thymidine into DNA and the concentration of cyclic AMP in renal cortex at all time points examined. The data demonstrate that even though the responsiveness of lung to subacute cadmium exposure differs from that of kidney cortex, the observed alterations in DNA synthesis may be mediated through modulation of cyclic AMP (and possibly polyamine levels) in both tissues.     

Changes in the levels of DNA methylation in testis and liver of SD rats neonatally exposed to 5-aza-2'-deoxycytidine and cadmium

To investigate the changes in the levels of DNA methylation in the testis during development after neonatal transient exposure to DNA methyltransferase (DNMT) inhibitors, we orally administered Sprague-Dawley (SD) rats with 5-aza-2'-deoxycytidine (5-aza-CdR; 0.025 or 0.25 mg kg(-1)) or cadmium (Cd; 1, 2 or 4 mg kg(-1)) daily from days 3-7 postpartum (pp). Sperm numbers decreased at day 70 pp in all exposure groups. We then used a PCR-based assay, combined bisulfite restriction analysis (COBRA) and pyrosequencing to determine the degrees of DNA methylation. Both 5-aza-CdR and Cd reduced DNMT activity in vivo after 5 days' exposure at day 8 pp but not at day 70 pp. In contrast, the DNA methylation level of LINE-1 was not changed in the testis, either at day 8 pp or at day 70 pp. We observed increased apoptosis and an increase in the p53 mRNA level, accompanied by a decreased DNA methylation level in the p53 gene promoter region, at day 8 pp in testis for the 5-aza-CdR-exposed groups but not in the Cd-exposed group. The Cd-exposed group exhibited a degradation of seminiferous tubules and inhibition of a stepwise change in methylation in the coding region of c-fos in testis at day 70 pp. Because we observed toxic phenotype development accompanied by aberrant DNA methylation, DNA methylation may play a role in chemical induced testis damage, with different DNMT inhibitors affecting DNA methylation levels in gene- or stage-specific manner.     

Lead exposure in pheochromocytoma cells induces persistent changes in amyloid precursor protein gene methylation patterns

It has been suggested that lead (Pb) exposure in early life may increase amyloid precursor protein (APP) expression and promote the pathogenesis of Alzheimer's disease in old age. The current study examined whether the DNA methylation patterns of APP gene in rat pheochromocytoma (PC12) cells changed after Pb acetate exposure. Undifferentiated PC12 cells were exposed to three doses of Pb acetate (50, 250, and 500 nM) and one control for 2 days or 1 week. The methylation patterns of APP promoter and global DNA methylation were analyzed. The DNA methyltransferase 1 (DNMT1) expression and the level of amyloid β peptide (Aβ) were also investigated. The results showed that the exposure of the three concentrations of Pb acetate could make the APP promoter hypomethylated. The global DNA methylation level and the expression of DNMT1 were changed in the 500 nM group after 2 days exposure and in the 250 and 500 nM group after 7 days exposure. Thus, Pb may exert neurotoxic effects through mechanisms that alter the global and promoter methylation patterns of APP gene. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

Activities of affinity-isolated glutathione S-transferase (GST) from channel catfish whole intestine

Tiger shrimp Penaeus monodon following 24 h exposure to 0.002 (control), 0.072 and 0.718 mM ammonia were examined for the free amino acid (FAA), ammonia and urea levels in the hemolymph, gill, hepatopancreas and muscle. Control shrimps contained total FAA in hemolymph (1.19 μmol ml(-1)), gill (21.81 μmol g(-1)), hepatopancreas (100.81 μmol g(-1)) and muscle (239.54 μmol g(-1)). Glycine and arginine were the major contributors to the total FAA pool, and made up of 90% of the total FAA in the muscle of P. monodon. The total FAA level in the hemolymph increased directly with ambient ammonia, whereas the total FAA level in the hepatopancreas was inversely related to ambient ammonia. No significant difference of total FAA was observed in the gill and muscle among the shrimps in three treatments. Ammonia level increased by 160% in hemolymph, 105% in gill, 236% in hepatopancreas and 68% in muscle for the shrimps exposed to 0.718 mM ammonia. Urea and ornithine in the hepatopancreas increased by 107 and 1446%, whereas arginine level in the hepatopancreas decreased by 50% for the 0.718 mM ammonia-exposed shrimps. Decreases of arginine and other FAA with a concomitant increase of ornithine and urea level in the hepatopancreas indicated catabolism of FAA and ureogenesis. Increases of ammonia, urea, taurine, glutamine, proline, alanine, glycine and asparagine in the hemolymph revealed a intracellular osmoregulation for P. monodon under the stress of ambient ammonia at 0.718 mM.     

Effect of pH on uptake,tissue distribution and retention of hexavalent chromium in rainbow trout (Salmo gairdneri)

Uptake, distribution and retention of chromium in rainbow trout (Salmo guirdneri) was studied after short-term (2–4 days) exposure to ⁵¹CrO₄^2? -containing Na₂CrO₄ solutions of different concentrations (2–50 mg/l Cr) and pH (7.8 and 6.5). At pH 7.8, highest contents of chromium were found in gill, liver, kidney, and digestive tract of the trout. Chromium was not distributed evenly among the different subcellular fractions of the tissues, but was concentrated in the nuclear fraction of the gill tissue and in the soluble fraction of the kidney and liver tissue. Upon transfer of exposed fish to tap-water, chromium was rapidly eliminated from blood, gill and digestive tract. However, chromium contents tended to remain high in kidney and liver. When the pH was decreased from 7.8 to 6.5, the lethal action of hexavalent chromium increased and a different pattern of accumulation and elimination of chromium was observed. The major differences were found in the gills, which concentrated significantly more chromium at pH 6.5 than at pH 7.8, irrespective of the exposure time and concentration. As an electronspin-resonance signal characteristic for trivalent or pentavalent chromium was detected in the gills, the differences must have been at least partly due to the higher oxidizing action of hexavalent chromium at the lower pH.     

Measurements of genotoxic potential of cadmium in different tissues of fresh water climbing perch Anabas testudineus (Bloch), using the comet assay

The present investigation was undertaken to study the induction of DNA damage by CdCl(2) in freshwater climbing perch Anabas testudineus (Bloch) using alkaline single cell gel electrophoresis (comet assay). The DNA damage was measured in the tissue of gill, kidney and liver as the percentage of DNA in comet tails and comet heads in the tissue of the fish specimens exposed to 0.1, 1.0, 2.0mgL(-1) concentrations of CdCl(2). It was found that at all the concentrations of CdCl(2), the liver tissue exhibited significantly (p<0.01) higher DNA damage, followed by kidney and gill tissue. The DNA damage was found to be concentration dependent, with the highest DNA damage at 2mgL(-1) concentration, followed by 1.0 and 0.1mgL(-1). At the concentration of 2mgL(-1) of CdCl(2), the tail and head DNA of liver tissue were 38.81% and 59.49%, in kidney tissue the values were 32.37% and 64.66% whereas in gill tissue the values were 31.30% and 66.40% respectively. This study conclude that comet assay can be used for in vivo laboratory experiment using fish as model for screening the genotoxic potential of cadmium.     

The changes to apical silver membrane uptake, and basolateral membrane silver export in the gills of rainbow trout (Oncorhynchus mykiss) on exposure to sublethal silver concentrations

Juvenile rainbow trout acclimated to softwater were exposed to 0 or 8.3 nM Ag (added as silver nitrate) for 21 days. On days 1, 7 and 21 gill, kidney and liver levels of silver; branchial Na+ influx, efflux and net flux rate; gill and kidney K+ -dependent p-nitrophenol phosphatase activity; and gill and liver accumulation of "new" Ag were measured. In addition, the concentration-dependent uptake of Ag by gill basolateral membrane vesicles (BLMV) was assessed in control fish and those exposed to 8.3 nM Ag for 7 days. Ag induced a significant increase in Na+ efflux following 1 day of exposure that resulted in an increase in net loss of Na+ and a reduction in Na+ influx. By day 21 this perturbation to Na+ balance had been corrected, but kidney K+ -dependent p-nitrophenol phosphatase activity was significantly reduced. Unexpectedly, the Ag concentrations in the liver of Ag exposed fish only significantly increased (two-fold) following 7 days of exposure and were not elevated when compared to controls on day 21. In contrast, the gill and kidney accumulated significant concentrations of Ag (20-fold increase) following 7 days of exposure, and the Ag concentration in these tissues remained similar on day 21. The gills of Ag exposed fish accumulated significantly less "new" Ag than the controls on days 7 and 21 following exposure, suggesting a down-regulation of branchial Ag uptake. The BLMV of Ag exposed fish showed a significant increase in V(max) [control fish BLMV V(max) = 2811.9+/-190.8 pmol (110 m)Ag/(mg protein x min) and Ag exposed fish BLMV V(max) = 3688.3+/-659.8 pmol (110 m)Ag/(mg protein x min) (P = 0.033)], suggesting that they are able to increase export of Ag from the gills on exposure to Ag. The results from this study demonstrate a complex array of physiological processes that control the bioreactive concentrations of Ag in the gills, including: cytoplasmic sequestration, a down-regulation of apical entry and potentially an increase in basolateral membrane extrusion.