Inhibition of rat serum polyphenoloxidase activity by silver ions abolished by administration of copper ions.

The administration of silver nitrate (6.47 mg, i.e. 60 mumol Ag+/rat/day) in food was followed in only two days by a pronounced decrease in polyphenoloxidase activity (ceruloplasmin) in rat serum. The administration of copper in the form of copper sulphate (12.7 mg, i.e. 200 mumol Cu2+/rat/day) raised polyphenoloxidase activity (the ceruloplasmin level), the increase being particularly marked on the first four days. On combining the two factors, the effect of Cu+ predominated throughout the duration of the experiment (32 days).