The action of heavy metals on the gametes of the marine mussel, Mytilus edulis (L.)--I. Copper-induced uncoupling of respiration in the unfertilized egg

The direct addition of Cu2+ to unfertilized eggs of Mytilus edulis results in a stimulation of respiration with maximal stimulation occurring at a Cu2+ concentration of ca 0.5 mM. By contrast, the addition of Zn2+ has no effect on egg respiration. The uncoupler CCCP produces a 5/6 fold stimulation of egg respiration but the addition of ADP leads to only a small release of respiration. In contrast, sperm respiration is unaffected by Cu2+, inhibited by Zn2+ and CCCP produces only a small respiratory stimulation. The addition of Cu2+ to respiring Mytilus mantle tissue mitochondria produces an initial stimulation of State 4 oxidation which is then followed by a progressive inhibition. It is suggested that respiration in the unfertilized egg may be inhibited by a high ATP/ADP ratio in the cytosol. Respiration can, therefore, be released by either the addition of a H+-translocating uncoupler or by Cu2+ which may act by stimulating mitochondrial K+ influx.