Movement of thallous ion across the ascites cell membrane

Abstract

The movement of thallous ion (Tl⁺ across the ascites cell membrane has been characterized. Analogous to previous findings for⁸⁶Rb⁺ (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.