Metallothionein induction in early larval stages of tilapia (Oreochromis mossambicus).
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.
Wu
S M
SM
Department of Aquaculture, National Chiayi Institute of Technology, Chiayi 600, Taiwan, Republic of China.
Weng
C F
CF
Hwang
J C
JC
Huang
C J
CJ
Hwang
P P
PP
D000818:Animals; D002104:Cadmium / Q000009:adverse effects*; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D008668:Metallothionein / Q000096:biosynthesis*; D017210:Tilapia / Q000502:physiology*; D014874:Water Pollutants, Chemical / Q000009:adverse effects*
D014874:Water Pollutants, Chemical; D002104:Cadmium; D008668:Metallothionein