Movement of thallous ion across the ascites cell membrane

The movement of thallous ion (Tl+) across the ascites cell membrane has been characterized. Analogous to previous findings for 86Rb (used as a tracer for K+), 204Tl+-influx could be resolved into three components: a ouabain-inhibitable "pump" flux, a passive flux, and a furosemide- or NO-3-sensitive "exchange" flux. Although Tl+ moved approximately nine times faster across the membrane than K+, the pump/leak ratio was equal for the two ions. This suggests that the pump- and leak-pathways share a common rate-limiting step. The exchange mechanism was shown to provide close coupling between the Tl+- and K+-gradients.