Copper effects on ion transport across lamprey erythrocyte membrane: Cl-/OH- exchange induced by cuprous ions

We studied the effects of prelytic copper concentrations on cell volume, in tracellular pH, and ion transport in lamprey erythrocytes. Ion fluxes and p H were measured by radioactive tracer technique, patch clamp, and flame pho tometry. Prelytic CuSO4 concentration of 100 mu M caused anion-dependent in tracellular acidification and increase in Cl- influx after 2 min lag-phase. In the presence of ascorbate copper effect was amplified and lag-phase was skipped. Pretreatment of the cells with N-phenyl maleimide abolished coppe r-induced changes completely. Copper treatment caused an increase in Na+ fl uxes in both directions and a net Na+ uptake. Copper-induced Na+ transport was partially amiloride(MIA)-sensitive representing Na+/H+ exchange. The na ture of the amiloride-insensitive fraction of copper-activated Na+ influx r emains unknown. Cell swelling after 15 min of copper exposure induced regul atory volume decrease response involving KCI extrusion via K+ and Cl- volum e-sensitive channels. We suggest that the effects of copper on ion transpor t fit the following sequence of events: (i) cupric ions are reduced to cupr ous state on the membrane surface, (ii) electroneutral pairs CuCl and CuOH mediate chloride/hydroxyl exchange, as shown before for trialkyltin, dissip ating transmembrane pH gradient, and (iii) changes in intracellular pH resu lt in the activation of the Na+/H+ exchange and consecutive volume changes cause the RVD response. (C) 1999 Academic Press.