Cadmium sorption to plasma membrane isolated from barley roots is impeded by copper association onto membranes

▶ Cadmium sorption to plasma membrane vesicles is impeded by Cu. ▶ Both permeation and association of Cd to plasma membrane vesicles occurred without energy source. ▶ Association of Cu to plasma membrane vesicles is quicker than Cd sorption. The present study was designed to examine the effect of copper (Cu) on sorption of cadmium (Cd) to plasma membrane (PM) preparations as one of the models of competition between metals on root PM. Plasma membrane preparations were obtained from roots of barley ( Hordeum vulgare L. cv. Minorimugi) and 50 μM CdSO 4 with or without 50 μM CuSO 4 were added to the PM suspensions. The sorption of Cd to PM vesicles increased with time within 15 min while Cu sorption to the PM occurred instantaneously. The sorption of Cd to PM vesicles was inactivated immediately after the addition of Cu into the reaction mixture. Results indicate that Cu association to PM vesicles occurs quicker than Cd, and, as a result, impedes the access of Cd to PM vesicles. The present study suggests that the competition between Cd and other minerals at root PM of plants can be demonstrated by employing isolated PM preparations. We consider that the difference in the capacity among some minerals for impeding Cd sorption to PM may also be characterized by investigating the interaction between Cd and other minerals on the PM.