Patel B, Chandy J P, Patel S
Health Physics Division, Bhabha Atomic Research Centre, Bombay, India.
Sci Total Environ. 1988 Oct 15;76(2-3):147-65. doi: 10.1016/0048-9697(88)90104-0.
The effect of selenium (SeO2) and glutathione (GSH) on the bioaccumulation of mercury (HgCl2) and on the activities of lysosomal enzymes in four species of tropical estuarine lamellibranchs is reported. A definite correlation between mercury levels in the external medium and tissue uptake and physiological behaviour--opening and closing of shell valves, response to mechanical stimulus, mucus secretion, and incidence of bleeding--was evident. In the clams exposed to Hg (range 0.1-5.0 mg l-1), bioaccumulation was dependent on the ambient concentration of Hg. The highest bioaccumulation of Hg occurred during the initial 24 h exposure period. Further exposure of up to 7 days did not increase the body burden of Hg. Of the four bivalve species exposed to 0.1 mg Hg l-1, Perna viridis showed the highest levels of Hg (approximately 47 ppm) followed by Anadara granosa, A. rhombea (approximately 25 ppm) and Meretrix casta (approximately 9 ppm). The uptake of Hg by A. granosa was greatly reduced by GSH, whereas Se enhanced it by 50% when administered in combination with Hg. However, the presence of Hg did not influence the uptake of Se. Exposure to combined GSH and Hg resulted in almost complete inhibition of Hg uptake in all four bivalve species. Prior exposure to GSH, however, did not have the same influence on their uptake of Hg. Nevertheless, exposure of clams to GSH following initial exposure to Hg resulted in complete depuration of accumulated Hg. The activities of lysosomal enzymes--arylsulfatase, acid phosphatase, beta-galactosidase and beta-glucuronidase--varied considerably. Treatment with Hg and GSH, separately and in combination, significantly enhanced the levels of beta-galactosidase (P less than 0.05) and beta-glucuronidase (P less than 0.001) in the digestive gland after 96 h exposure. Although Se increased beta-glucuronidase activity (P less than 0.001), it had no effect on beta-galactosidase. On exposure to Hg + Se the activity of both enzymes decreased, except in P. viridis where it increased by 39%. The results show unequivocally that Se does not offer any protection against the toxic effects of mercury in marine lamellibranchs, whereas in many marine vertebrates it does. GSH, a thiol-rich tripeptide, on the other hand, completely nullifies the toxic effects of Hg, both in vivo and in vitro.
本文报道了硒（二氧化硒）和谷胱甘肽对四种热带河口双壳贝类生物累积汞（氯化汞）以及溶酶体酶活性的影响。外部介质中的汞含量与组织摄取量及生理行为（如贝壳开合、对机械刺激的反应、黏液分泌和出血发生率）之间存在明显的相关性。在暴露于汞（浓度范围为0.1 - 5.0毫克/升）的蛤类中，生物累积量取决于环境中的汞浓度。汞的最高生物累积量出现在最初的24小时暴露期。进一步暴露长达7天并未增加汞的体内负荷。在暴露于0.1毫克/升汞的四种双壳贝类中，翡翠贻贝的汞含量最高（约47 ppm），其次是颗粒蚶、菱形蚶（约25 ppm）和中国蛤蜊（约9 ppm）。谷胱甘肽极大地降低了颗粒蚶对汞的摄取，而硒与汞联合使用时则使其摄取量增加了50%。然而，汞的存在并不影响硒的摄取。联合暴露于谷胱甘肽和汞导致所有四种双壳贝类对汞的摄取几乎完全受到抑制。然而，预先暴露于谷胱甘肽对它们摄取汞的影响并不相同。尽管如此，在最初暴露于汞后再让蛤类暴露于谷胱甘肽会导致累积的汞完全排出。溶酶体酶（芳基硫酸酯酶、酸性磷酸酶、β - 半乳糖苷酶和β - 葡萄糖醛酸酶）的活性差异很大。在暴露96小时后，单独及联合使用汞和谷胱甘肽处理显著提高了消化腺中β - 半乳糖苷酶（P < 0.05）和β - 葡萄糖醛酸酶（P < 0.001）的水平。虽然硒增加了β - 葡萄糖醛酸酶的活性（P < 0.001），但对β - 半乳糖苷酶没有影响。暴露于汞 + 硒时，除翡翠贻贝中这两种酶的活性增加了39%外，其他情况下两种酶的活性均下降。结果明确表明，在海洋双壳贝类中，硒并不能对汞的毒性作用提供任何保护，而在许多海洋脊椎动物中它却能。另一方面，富含硫醇的三肽谷胱甘肽在体内和体外都能完全消除汞的毒性作用。
