金鱼(Carassius auratus L.)对水中游离态铅的吸收积累及鳃分泌粘液的自身保护作用

Uptake and accumulation of free lead by goldfish ( Carassius auratus L.) and effect of gill mucus on the processes

研究了金鱼（ Ｃａｒａｓｓｉｕｓａｕｒａｔｕｓ Ｌ．） 在铅暴露实验中的铅吸收过程及鱼鳃分泌物的自身保护作用、水相Ｐｂ２＋ 的鳃吸收机理以及分泌粘液对铅的络合作用．结果表明，金鱼因铅暴露导致粘液分泌量增加．结合到鳃上的铅与水相Ｐｂ２＋ 活度关系可用Ｌａｎｇｍｕｉｒ 吸附等温式表述．据此估算的最大结合量为０－９４２４ ｍ ｍｏｌ／ｋｇ（干重） ．非常接近１ 的Ｈｉｌｌ 常数（１－０１２）说明金鱼鳃上仅有一种类型的Ｐｂ２＋ 结合位点．平均每尾金鱼鳃上Ｐｂ２＋ 的结合位点数达１－６２ ×１０－ ５ ｍ ｍｏｌ，结合的条件稳定常数（ｌｏｇ ＫＰｂ鳃） 为４－８ ．血液铅含量与鳃铅含量间呈显著线性关系．金鱼吸收Ｐｂ２＋ 的主要过程为：Ｐｂ２＋ 结合到鳃上，其后被动扩散或载体转运穿过鳃上皮，进入血液循环．

Uptake of lead by goldfish ( Carassius auratus L.) and the effect of mucus on the uptake were studied. The mechanisms of lead uptake are discussed. It was demonstrated that the quantity of mucus released from the fish gill increased with the increasing in lead concentration in water and exposure duration. The mucus is capable of binding metals. Lead accumulated in gill was positively proportional to the lead level in water at low concentration (total lead less than 0.6mg/L). The plot of gill lead against water lead leveled off with increased lead concentration. A Langmuir isotherm can fit the observed data well and the saturated sorption capacity was calculated as 0.9424 mmol/kg (dry wt.). The binding cooperativity ( H n ) is very close to unit (1.012) indicating independent binding to the sites with unique apparent affinity. On average, the number of binding sites on the gill of each fish (96.0 mg,wet wt.) was estimated to be 1.62×10 -5 mmol with a conditional binding constant (log K Pb\|gill ) of 4.8. A significant linear relation of lead concentrations between gill and blood was observed during the 10\|day experiment, suggesting that the free lead in water is first bound on fish gill, then migrate across branchial epithelium to blood via passive diffusion or carrier transport.