Sodium Is Not Required for Chloride Efflux via ChlorideBicarbonate Exchanger from Rat Thymic Lymphocytes

Abstract EN

Sodium-dependent Cl−/HCO3- exchanger acts as a chloride (Cl−) efflux in lymphocytes.

Its functional characterization had been described when Cl− efflux was measured upon substituting extracellular sodium (Na+) by N-methyl-D-glucamine (NMDG).

For Na+ and Cl− substitution, we have used D-mannitol or NMDG.

Thymocytes of male Wistar rats aged 7–9 weeks were used and intracellular Cl− was measured by spectrofluorimetry using MQAE dye in bicarbonate buffers.

Chloride efflux was measured in a Cl−-free buffer (Cl− substituted with isethionate acid) and in Na+ and Cl−-free buffer with D-mannitol or with NMDG.

The data have shown that Cl− efflux is mediated in the absence of Na+ in a solution containing D-mannitol and is inhibited by H2DIDS.

Mathematical modelling has shown that Cl− efflux mathematical model parameters (relative membrane permeability, relative rate of exchanger transition, and exchanger efficacy) were the same in control and in the medium in which Na+ had been substituted by D-mannitol.

The net Cl− efflux was completely blocked in the NMDG buffer.

The same blockage of Cl− efflux was caused by H2DIDS.

The study results allow concluding that Na+ is not required for Cl− efflux via Cl−/HCO3- exchanger.

NMDG in buffers cannot be used for substituting Na+ because NMDG inhibits the exchanger.