Renal responses to potassium restriction depend on dietary sodium

Abstract

Previous studies of renal responses to dietary potassium (K) restriction compared control chow containing 0.74%NaCl with and without 2% KCl.Aimre‐examine renal responses to K restriction with 2% NaCl chow, the % found in the average American diet. Sprague Dawley rats (n=4‐6) were fed one of these diets 6 d: control chow CKCNa= 2%KCl‐0.74%NaCl, low K chow LKCNa = 0.05%KCl‐0.74%NaCl, high Na chow CKHNa= 2%KCl‐2%NaCl, low K high Na chow LKHNa= 0.05%KCl‐2%NaCl. Rats were placed in metabolic cages overnight, anesthetized for BP, sacrificed, and kidneys removed. Plasma [K] fell from 3.8 to 2.4 mM and [Na] remained at 140 mM in both LKCNa and LKHNa. Compared to LKCNa, LKHNa gained twice as much weight (6 vs 3 g/d), had lower BP (93 vs 101 mmHg) and higher urine osmolality (500 vs 325 mOsm). In renal homogenates of LKCNa vs CKCNa, as previously reported, pool size of NHE3, HK‐ATPase(g) and HK‐ATPase(c) and NaK‐ATPase(b) were increased and pool size of ROMK, ENaC(b) and AQP2 were decreased. In LKHNa vs CKHNa pool size of ROMK and ENaC(b) were reduced but NHE3, HK‐ATPases, NaK‐ATPase, AQP2 were unchanged.Conclusiondietary K restriction and/or hypokalemia provoke BP to fall and decrease ROMK and ENaC abundance which are key to conserving K. The additional physiologic and transporter changes seen with lower NaCl diet may be secondary to drastically lowering total electrolytes and/or chloride. DK34316 and UKRO fellowship to LEY.