The Na⁺-K⁺-Cl⁻ cotransporter type 2 (NKCC2) belongs to the cation-Cl⁻ cotransporter (CCC) family. It exists as three splice variants called A, B and F that differ among each other by 32 residues and that are all localized on the apical membrane of the thick ascending loop of Henle (TALH) as homodimers. However, they are differentially distributed along this nephron segment: NKCC2F is localized in the initial part of the TALH where it ensures substantial NaCl reabsorption to maintain the extracellular fluid volume and NKCC2A and NKCC2B are localized in the distal part of the TALH where it ensure more modest NaCl reabsorption to help in the maintenance of the extracellular fluid volume and support the tubuloglomerular feedback. As "A" and "B" are localized in the same cellular types, we asked ourselves: 1) whether they could form AB heterodimers with transport characteristics that differ from AA and BB and 2) whether the relative quantities of AA, AB and BB formed could be regulated to allow the distal TALH and macula densa to operate adequately within a wider range of ionic concentrations. My research objective was thus to generate cDNA constructs in which the A and/or B variants are connected to each other by an inert "linker" to force the formation of AA, AB or BB by proximity, to express the product of these cDNA constructs in Xenopus laevis oocytes and to characterize the transport kinetics of the NKCC2 produced. We found that AB heterodimers exhibited unique functional characteristics (relative to AA or BB). In particular, maximal transport rates were much higher for the AB heterodimers than for the AA and BB homodimers. Our data therefore suggest that the assembled subunits cooperate with each other during the transport cycle. Our data also pave the way towards the possibility that the quantity of AB heterodimers formed is regulated such that an array of responses are allowed as a function of the needs to be met.