Effect of cadmium and zinc on the Na+/H+ exchanger present on the brush border membrane vesicles isolated from eel kidney tubular cells.

The present paper reports evidence on the effect of cadmium and zinc on the Na+/H+ exchanger activity located on the apical membranes of the eel kidney tubular cells. The activity of the exchanger, as well as the membrane vesicle permeability to protons, were monitored by using the pH sensitive dye acridine orange. The membrane vesicle permeability to sodium ions was tested either by using the potential sensitive dye DiS–C2(5) or by using 22Na coupled with the rapid filtration technique. Results indicate that both cadmium and zinc inhibited, in a dose-dependent manner, the activity of the exchanger. However, at the higher tested concentration (0.1 mM) the inhibitory effect exerted by Zinc (90% of inhibition with respect to the control value obtained in the absence of zinc) was significantly (P