Abstract
Attempts were made to elucidate the protective mechanism against acute cadmium toxicity in the rainbow trout which was previously exposed to a cadmium solution at low concentration.
Fish specimens weighing about 130g, which were previously kept in tap water or 0.009ppm cadmium solution for 15 days, were intraperitoneally administered with 0.75mg of cadmium per kg body weight. During pretreatment with cadmium, this metal accumulated in the liver, kidney, gill, intestine and vertebrae of the fish. Liver and kidney extract of the cadmium exposed speci-wens gave rise to two distinct peaks of metallothionein when subjected to gel chromatography. The level of metallothionein thus induced was higher in kidney than in liver. Asubsequent ad-ministration of high level of cadmium inhibited alkaline phosphatase in serum and lowered calcium levels in serum and vertebrae. On the other hand, pretreatment with cadmium prevented these toxicological changes.
Kidney metallothionein was supposed to be responsible for the increased tolerance against cadmium toxicity of rainbow trout pretreated with a low level of this metal.
