Influence of chronic Cd intoxication on the alkaline phosphatase activity of liver and kidney; biochemical, histochemical and histological investigations.

To distinguish between: (a) the decrease of activity of alkaline phosphatase due to inhibition by cadmium; and (b) the decline of enzyme activity due to cell destruction, 20 adult female Wistar rats were treated 3 times/week with 0.5 mg/kg CdCl2 (by subcutaneous injection) during 28 weeks. Controls received the same volume of 0.9% NaCl solution. The animals were killed at different intervals. The liver and kidneys were investigated with biochemical, histochemical, light and electron microscopical techniques. The liver homogenates show an increase of alkaline phosphatase activity after about 12-13 weeks, whereas the activity of this enzyme in the kidney decreases. This activity could not be restored by the administration of Zn ions to the medium of the enzyme assay. However, in previous in vitro experiments the Cd inhibited alkaline phosphatase activity could be totally restored by such a Zn administration. By histochemical assay of alkaline phosphatase in the renal cortex a decrease of enzyme activity was demonstrated. By evaluation of the results obtained with light and electron microscopy, in combination with the biochemical results, the decrease of alkaline phosphatase activity in the kidney should be considered as a real decrease in the amount of this enzyme due to cell degeneration.