钠抗镉对水生物毒性及吸收动力学的研究

Sodium Antagonizes the Toxicity and Uptake of Cadmium in T. Tubifex

测定Cd以及Cd在NaCl存在时对水蚯蚓（T.Tubifex）的毒性,并用^(109)Cd^(2+)标记测定水蚯蚓对Cd^(2+)吸收速度。实验发现随着Na^+变化Cd半致死量LC_(50)也发生变化,当Na^+浓度增加到8.0×10^(-2)mol·L^(-1)时,在48h时,毒性下降了21倍;在低于1.0×10^(-3)mol·L^(-1)NaCl时,水蚯蚓对Cd^(2+)吸收速度没有明显的变化,可当NaCl浓度大于1.0×10^(-2)mol·L(-1)时有明显下降（P<0.05）。用Lineweave-Burk法处理实验数据得到最大吸收速度V_max和米氏常数K_m,当Na^+提高时V_max基本保持为常数(5.5-7.5)×10^(-7)mol·g^(-1)·h^(-1),而K_m成倍增加,这表明Cd^（2+）和Na^+竞争相同的转移通道进入动物体内,从而导致影响Cd对水蚯蚓的毒性。

The acute toxicity of CdCl2alone or in combination with NaCl was determined in T. Tubifex. . The values of the LC50 of Cd were significantly different with varied concentrations of Na ions. The toxicity decreased 21-fold at 48hafter adding Na+ up to 80.0 mmol/L. The rate of Cd uptake in T. tubifex was measured by incubation with 109 Cd2+.Cd2 uptake in worms did not change significant below 1.0 mmol/L NaCl, however, above 10 mmol/L NaCl there was a decrease (P < 0.05) compared to the controls (0.0 mmol/L NaCl) . Using the Lineweaver - Burk method, vmax is found constant about (5.5 - 7.5)×10~ mol. g ~ .h ~ and the apparent Km values increased from 21.3 umol/L at 0 .0 mmol/L NaCl to 83.2 and 573μmol/L at 10.0 and 80 mmol/L NaCl, respectively. This suggests that Cd2+ may compete with Na+ for the same transport site which may lead to influence of cadmium to this worm.