Changes in the sodium and potassium transporters in the course of chronic renal failure.

Background: In chronic renal failure (CRF), residual nephrons can increase their excretion of sodium (Na) and potassium (K). However, the mechanisms of renal Na and K regulation in late-stage CRF have not been clearly investigated.

Methods: We examined altered expression of major renal Na and K transporters in Sprague-Dawley rats at 4 and 12 weeks after a 5/6 nephrectomy.

Results: CRF rats were azotemic and had gradually increased levels of urinary Na and K excretion over time. At 4 weeks, the abundance of Na-K-2Cl cotransporter (NKCC2), and Na-Cl cotransporter (NCC) in CRF rats increased significantly (477 and 222% of the control, respectively). In contrast, expression of NKCC2 and NCC decreased markedly at 12 weeks (55.4 and 30.8%, respectively). Expression of epithelial Na channel-alpha increased throughout the whole period. The abundance of renal outer medullary K-channel (ROMK) and Na-K-ATPase did not decrease at 4 weeks, but it was reduced at 12 weeks.

Conclusions: We suggest that increased urinary Na excretion in late-stage CRF may be associated with decreased expression of renal Na transporters except ENaC compared to early-stage CRF, and that increased urinary K excretion in the late stage of CRF may not be related to expression of ROMK.