Altered expression renal Na+ transporters and ROMK in protein-deprived rats

RUETE MC; CARRIZO LC; BOCANEGRA MV; VALLÉS P

Nephron Physiology

Año: 2009 vol. 111 p. 17 - 29

Potassium depletion has been associated with altered sodi-um reabsorption in tubule segments. We studied if the al-tered abundance of Na+ transporters and ROMK are associ-ated with distal potassium secretion that contributes to thedevelopment of hypokalemia in protein-deprived rats. Afterweaning, Wistar rats were fed with a low-protein diet (8%,LP) for 14 days and then recovered with a normal-protein(NP) diet (24%, RP). An age-matched control group was fedwith an NP diet (24%, NP). We showed hypokalemia, lowerglomerular filtration rate and higher FEK+ in the LP group.Immunoblotting revealed that the type 3 Na+/H+ exchangerin the cortex was decreased in the LP group. However, thetype 2 Na+-K+-2Cl– cotransporter was increased in the outerstripe of the outer medulla in the LP group. The abundanceof the aldosterone-regulated Na+-Cl– cotransporter (NCC)and epithelial Na+ channel (ENaC) was higher in the LP groupand was associated with higher plasma aldosterone level.ROMK protein levels were increased. Na+/K+-ATPase proteinlevels were the same in both groups. After the recovery pe-riod, the expression of Na+ transporters and ROMK returnedto control values. We conclude that increased expression ofNCC, ENaC subunits, and ROMK contributed to distal potas-sium secretion leading to enhanced potassium excretion,which may explain the hypokalemia resulting from LP feed-ing. A role of aldosterone may be suggested.