The suggestion has been put forward that the oligodynamic action of certain heavy metals is the result of the destruction or inactivation of substances essential for cellular respiration. In a study of the effect of copper sulphate solutions on the oxygen consumption of Polycelis nigra it is found that solutions of concentration 0.001-0.01 N, fatal in 2 hr. or less, induce a marked preliminary rise in the respiration rate; this appears to be due to the inhibition of ciliary locomation and increased muscular activity. A similar increase is produced by increasing the activity of the animals by mechanical means, or by a muscle stimulant (barium chloride). Over the latter part of the survival time the respiration rate drops rapidly and disintegration of the animals begins when it falls to about 60% of the normal value. A 0.0004 N copper sulphate solutions does not inhibit ciliary locomotion, does not stimulate muscular activity, and the oxygen consumption undergoes a stedy decline. A 0.0002 N NaCN solution rapidly depresses the respiration rate to less than 20% of the normal value, but is not fatal, the animals surviving over 4 days. Hydrogen ions, at the concentrations resulting from the hydrolysis of the salt, have no appreciable effect on the oxygen consumption, but at lethal concentrations (pH 2.6, 2.8) effect a speedy depression. The results suggest that the depression of respiration rate observed is insufficient to account for the death of the animals, and is no more than a symptom of the toxic process.
A similar general result was obtained in experiments with silver nitrate and mercuric chloride, and also in experiments on the comparative effect of copper sulphate and sodium cyanide solutions on the oxygen consumption of Gammarus pulex.
The Effect of Ionic Copper on the Oxygen Consumption of Gammarus Pulex and Polycelis Nigra