Tumor necrosis factor-[alpha] is an endogenous inhibitor of Na+-K+-2Cl-cotransporter (NKCC2) isoform A in the thick ascending limb

The effects of TNF gene deletion on renal Na+-K+-2Cl... cotransporter (NKCC2) expression and activity were determined. Outer medulla from ... mice exhibited a twofold increase in total NKCC2 protein expression compared with wild-type (WT) mice. This increase was not observed in ... mice treated with recombinant human TNF (hTNF) for 7 days. Administration of hTNF had no effect on total NKCC2 expression in WT mice. A fourfold increase in NKCC2A mRNA accumulation was observed in outer medulla from ... compared with WT mice; NKCC2F and NKCC2B mRNA accumulation was similar between genotypes. The increase in NKCC2A mRNA accumulation was attenuated when ... mice were treated with hTNF. Bumetanide-sensitive O... consumption, an in vitro correlate of NKCC2 activity, was 2.8 ± 0.2 nmol-min...-mg... in medullary thick ascending limb tubules from WT, representing ~40% of total O... consumption, whereas, in medullary thick ascending limb tubules from ... mice, it was 5.6 ± 0.3 nmol...-in...-mg..., representing ~60% of total O... consumption. Administration of hTNF to ... mice restored the bumetanide-sensitive component to ~30% of total O... consumption. Ambient urine osmolality was higher in ... compared with WT mice (2,072 ± 104 vs. 1,696 ± 153 mosmol/kgH...O, P < 0.05). The diluting ability of the kidney, assessed by measuring urine osmolality before and after 1 h of water loading also was greater in ... compared with WT mice (174 ± 38 and 465 ± 81 mosmol/kgH...O, respectively, P < 0.01). Collectively, these findings suggest that TNF plays a role as an endogenous inhibitor of NKCC2 expression and function. (ProQuest: ... denotes formulae/symbols omitted.)