Action of cadmium on the gills of Carassius auratus L. in presence of catabolic NH3.

Histochemical changes of oxidative enzymes and cadmium uptake in the Carassius auratus gills were examined up to 7 days after a 87.6 mu M cadmium exposure in very alkaline water in the presence and absence of catabolic ammonia. In the presence of catabolic NH3, the toxic action of cadmium is much more intense and determines a 20% survival of goldfish with a heavy increase in the excretion of mucus. Animals treated with cadmium only and controls survived in the order of 100%. More drastic histochemical alterations in the activity of oxidative enzymes (SDH, G-6-PDH, LDH) were documented in animals treated both with cadmium and ammonia, if compared with those treated with cadmium only. A reduction in the activity of enzymes after 24 h, a heavy increase of the LDH reaction after 72 h, and a strong increase after 7 days in the number of positive SDH cells (which correspond to chloride cells) were documented. After a hyperaccumulation at 24 h (returning afterwards to much lower values), at 7 days the cadmium uptake was higher in the animals treated both with cadmium and ammonia.