Effects of lead, copper, and zinc on the rat's lactate dehydrogenase in vivo and in vitro.

Following subacute intoxication of rats with Pb-, Cu-, and Zn-salts (separately or in mixture) for 5 weeks, the chelating agent D-penicillamine was administered for 3 weeks. In the course of the 3-month experiment, lactate dehydrogenase (LDH) was estimated in serum and in cytoplasmic fraction of the kidney. Pb2+ treatment resulted in an increase of LDH activity, Cu2+ in a slight decrease, whereas Zn2+ had no effect, respectively. Mixture of these metals caused a significant rise in the enzymatic activity. Seven weeks after the stoppage of the administration of toxic substances, altered LDH activity, both in serum and in kidney returned to normal. D-penicillamine treatment was found to accelerate a restoration of the enzyme activity. In the experiments in vitro, Cu2+ inhibited significantly the kidney LDH activity, Pb2+ and Zn2+ being 100- and 400-times less efficient, respectively. Cu2+ inhibition was reversed by D-penicillamine, whereas inhibition of LDH by Zn2+ or Pb2+ was irreversible.