Wu S M, Weng C F, Hwang J C, Huang C J, Hwang P P
Department of Aquaculture, National Chiayi Institute of Technology, Chiayi 600, Taiwan, Republic of China.
Physiol Biochem Zool. 2000 Sep-Oct;73(5):531-7. doi: 10.1086/317754.
Amounts of whole-body metallothionein (MT) in tilapia (Oreochromis mossambicus) larvae increased to a peak (1,500 ng mg(-1) protein) 1 d after hatching (H1), decreased rapidly thereafter, and was maintained at a constant level (700 ng mg(-1)) 3 d after hatching (H3). Waterborne Cd(2+) could stimulate MT expression in newly hatched (H0) larvae in dose-dependent and time-dependent patterns. H0 larvae, which were treated with 35 microg L(-1) Cd(2+) for 24 h, showed a 1.7-fold increase in the MT amount (174.0+/-64.7) and a 6. 5-fold increase in accumulated Cd(2+) but no significant change in Ca(2+) content, compared with the H0 control (MT, 102.6+/-48.1). H3 larvae with the same treatment revealed about a 10-fold increase in accumulated Cd(2+), a 10% decrease in Ca(2+) content, but no change in MT (261.2+/-120.0), compared with the H3 control (MT, 330+/-74.0). H0 larvae could synthesize more MT to bind Cd(2+) for detoxification in 35 microg L(-1) Cd(2+), a dose that would not affect normal physiology or survival of H0 larvae. On the other hand, 35 microg L(-1) Cd(2+) caused H3 larvae to experience hypocalcemia, an abnormal physiological condition, in which H3 larvae could not synthesize sufficient MT, thus causing greater than 25% mortality. These results indicate for the first time that the inducibility of MT by waterborne Cd(2+) is development dependent, being correlated with inconsistent sensitivities to Cd(2+) during larval development.
莫桑比克罗非鱼（Oreochromis mossambicus）幼鱼体内的全身金属硫蛋白（MT）含量在孵化后1天（H1）增加至峰值（1500 ng mg⁻¹蛋白质），此后迅速下降，并在孵化后3天（H3）维持在恒定水平（700 ng mg⁻¹）。水体中的Cd²⁺能以剂量依赖性和时间依赖性模式刺激新孵化（H0）幼鱼的MT表达。与H0对照组（MT，102.6±48.1）相比，用35 μg L⁻¹ Cd²⁺处理24小时的H0幼鱼，MT含量增加了1.7倍（174.0±64.7），累积的Cd²⁺增加了6.5倍，但Ca²⁺含量无显著变化。相同处理的H3幼鱼与H3对照组（MT，330±74.0）相比，累积的Cd²⁺增加了约10倍，Ca²⁺含量降低了10%，但MT无变化（261.2±120.0）。H0幼鱼在35 μg L⁻¹ Cd²⁺中能合成更多MT来结合Cd²⁺进行解毒，该剂量不会影响H0幼鱼的正常生理或存活。另一方面，35 μg L⁻¹ Cd²⁺导致H3幼鱼出现低钙血症，这是一种异常生理状况，其中H3幼鱼无法合成足够的MT，从而导致死亡率超过25%。这些结果首次表明，水体Cd²⁺对MT的诱导能力具有发育依赖性，与幼鱼发育过程中对Cd²⁺的敏感性不一致相关。
