Functional Properties of the Apical Na+-K+-2Cl− Cotransporter Isoforms

摘要: Abstract The bumetanide-sensitive Na+:K+:2Cl− cotransporter (BSC1) is the major pathway for salt reabsorption in apical membrane of mammalian thick ascending limb Henle. Three isoforms cotransporter, known as A, B, and F, exhibit axial expression along limb. We report here a functional comparison three from mouse kidney. When expressed inXenopus oocytes mBSC1-A isoform showed higher capacity transport, with no difference amount surface expression. Kinetic characterization revealed divergent affinities cotransported ions. observed EC50 values Na+, K+, Cl− were 5.0 ± 3.9, 0.96 0.16, 22.2 4.8 mm mBSC1-A; 3.0 0.6, 0.76 0.07, 11.6 0.7 mBSC1-B; 20.6 7.2, 1.54 29.2 2.1 mBSC1-F, respectively. Bumetanide sensitivity was mBSC1-B compared mBSC1-F isoforms. All transporters partially inhibited by hypotonicity but to different extents. cell swelling-induced inhibition profile > mBSC1-A. function Na+:K+:2Cl−cotransporter not affected extracellular pH or addition metolazone, 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS), orR(+)-[(2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1-H-indenyl-5-yl)-oxy]acetic (DIOA) medium. In contrast, exposure HgCl2 before uptake period reduced activity cotransporter. effect dose-dependent, exhibited affinity than mBSC1-F. Overall, murine renal-specific F reveals important functional, pharmacological, kinetic differences, both physiological structural implications.