Hypokalemia in Low Protein Feeding (LP). Altered Expression of Major Renal Na+ and K+ Transporters

RUETE MC; VALLES P

Budapest, Hungary

Congreso; 14th Congress of The International Pediatric Nephrology Association; 2007

The direction and magnitude of potassium transport in nephron segments depend on the sitespecific distribution of transporters in tubule cell membranes. Potassium depletion has been demonstrated to be associated with altered sodium reabsorption in renal tubule segments. We examined whe her potassium transporters protein expression is associated with altered abundance of major renal Na+ transporters, that may contribute to the development of hypokalemia in LP. After weaning rats (n=8) were fed 14 days with LP diet (8%), then they were recovered with a normal protein diet (24%, RP), each group had a control group (24%, NP). We examined the changes in the abundance of the Na+/H+ exchanger (NHE3), Na+K+ATPase, Na+K+2Cl- cotransporter (BSC-1), Na+Cl- cotransporter (TSC), epithelial sodium channel (ENaC) subunits and ROMK in kidneys of LP, NP, RP rats. Controls were normalized to 1. Results Reduced Clcreat (ml/min) in LP vsNP (0.6±0.2 vs 1.6±0.2), hypokalemia (3.6±0.1 vs 5.1±0.2 mEq/L) and increased FEK+ (44.2±0.5 vs 29.9±0.3%) were demonstrated. Immunoblotting revealed that the abundance of NHE3 in cortex was severely decreased. The amount of BSC-1 (1.9±0.07, p<0.05) and TSC (1.4±0.15, p<0.05) protein levels were enhanced in the inner stripe (ISOM) and outer stripe of the outer medulla (OSOM), respectively. ROMK protein levels were increased in LP (1.23±0.04, p<0.05), the protein abundance of the ENaC subunits α, β and γ was increased near 1.25 fold each in response to LP. Na+K+ATPase protein levels showed no differences in cortex and OSOM. After RP, Na+ transporters expression returned to control values.Conclusion: Increased expression of BSC-1, TSC, ENaC subunits and ROMK, contributing to distal potassium secretion was shown in hypokalemia from LP. A role of Aldosterone may be suggested.