ACTION OF CADMIUM ON THE GILLS OF CARASSIUS-AURATUS L IN THE PRESENCEOF CATABOLIC NH3

Histochemical changes of oxidative enzymes and cadmium uptake in the C arassius auratus gills were examined up to 7 days after a 87.6 mu M ca dmium exposure in very alkaline water in the presence and absence of c atabolic ammonia. In the presence of catabolic NH3, the toxic action o f cadmium is much more intense and determines a 20% survival of goldfi sh with a heavy increase in the excretion of mucus. Animals treated wi th cadmium only and controls survived in the order of 100%. More drast ic histochemical alterations in the activity of oxidative enzymes (SDH , G-6-PDH, LDH) were documented in animals treated both with cadmium a nd ammonia, if compared with those treated with cadmium only. A reduct ion 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 docum ented. 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. The authors assume that these effects should be ascribed to the complexation of cadmium with catabol ic ammonia.