Using the patch-clamp technique, two different ion channels have been characterized further in the human red blood cell (RBC) membrane. We demonstrate that the non-selective cation channel (NSC) is permeable to Ca(2+) and can be activated by prostaglandin E(2) (PGE(2)). Therefore, the physiological role of this channel could be, together with the Ca(2+)-activated K(+) channel, the participation in the process of blood clot formation. We give also evidence that another channel in the RBC membrane, so far assumed to be a small conductance anion channel, is more likely to be a proton or a hydroxyl ion channel.