Activation of the bumetanide-sensitive [Na.sup.+], [K.sup.+], 2[Cl.sup.-] cotransporter (NKCC2
) is facilitated by Tamm-Horsfall protein in a chloride-sensitive manner.
Because one of the mutations only partially impaired NKCC2
function, variable degrees of NKCC2
dysfunction may explain a mild and late-onset phenotype.
As for NKCC2
, patients with class II DN showed significantly higher uNKCC2 only compared with DM patients but not with CTR or DN (Figure 5(c)).
Abbreviations AQP2: Aquaporin 2 CNIs: Calcineurin inhibitors NKCC2
: [Na.sup.+]-[K.sup.+] -2[Cl.sup.-]-cotransporter ICU: Pediatric intensive care unit PRSL: Potential renal solute load RTA: Renal tubular acidosis.
Sodium transporter proteins, such as [Na.sup.+]/[H.sup.+] exchanger type 3 (NHE3), NKCC2
, and thiazide-sensitive [Na.sup.+]-[Cl.sup.-] cotransporter, are excreted in urine as previous studies have demonstrated .
Friedman and Herbert (1990) have suggested that the marine shark intermediate IV bundle zone segment is a "diluting segment" with low water permeability but high NaCl re-absorption via a NKCC2
cotransporter protein in the apical membrane of renal tubule cells.
(3) The increase in the expression of NKCC2
can occur as a compensatory mechanism.
 Nonstandard abbreviations: Cn, calcineurin; NFAT, nuclear factor of activated T cells; IL-2, interleukin 2; CnI, Cn inhibitor; CsA, cyclosporin A; RCAN1, regulator of calcineurin 1; DYRK1A, dual-specificity tyrosine phosphorylation--regulated kinase 1A; AD, Alzheimer disease; TGF-[beta], transforming growth factor [beta]; TRPC, transient receptor potential channel; COX-2, cyclooxygenase 2; NKCC2
, [Na.sup.+]-[K.sup.+]-2[Cl.sup.-] cotransporter 2; CREBc, AMP-response element--binding protein; NGAL, neutrophil gelatinase--associated lipocalin; KIM-1, kidney injury molecule 1; CTGF, connective tissue growth factor; BMP-7, bone morphogenetic protein 7.
A common NKCC2
mutation in Costa Rican Bartter's syndrome patients: evidence for a founder effect.
Pathologicaly the primary defect is impairment in one of the transporters involved in sodium chloride reabsorption in the thick ascending limb of loop of Henle or distal convoluted tubule viz, Na-K-2Cl cotransporter (NKCC2
) or apical K channel (ROMK) or basolateral chloride channel (ClCNKB).6 Defect in these channels leads to impaired absorption of Na+, K+, Cl- and calcium in thick ascending loop of Henle.