Effects of Furosemide and Ethacrynic Acid on Cation Transport Across Phospholipid Bilayer Membranes

Abstract

Phosphatidylcholine vesicles acquire a negative surface charge in the presence of furosemide or ethacrynic acid. In addition, these same vesicles also display a higher efflux rate for ²²Na and ⁸⁶Rb when exposed to these two diuretics. The experiments reported in this study indicate that the increased cation permeability is due to the creation of this negative surface charge. Cations will accumulate in the electrical double layer adjacent to the interface, resulting in a larger trans-membrane flux. In addition, ethacrynic acid also facilitates H⁺ transport in these vesicles, a property not shared by furosemide. Although the explanation for the enhanced H⁺ permeability is unclear, the experiments indicate that it occurs through a different mechanism than that by which alkali-metal cation movement is increased.