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Extracellular fluid (ECF) potassium concentration ([K+]) is maintained by adaptations of kidney and skeletal muscle, responses heretofore studied separately. We aimed to determine how these organ systems work in concert to preserve ECF [K+] in male C57BL/6J mice fed a K+-deficient diet (0K) versus 1% K+ diet (1K) for 10 days ( n = 5–6/group). During 0K feeding, plasma [K+] fell from 4.5 to 2 mM; hindlimb muscle (gastrocnemius and soleus) lost 28 mM K+ (from 115 ± 2 to 87 ± 2 mM) and gained 27 mM Na+ (from 27 ± 0.4 to 54 ± 2 mM). Doubling of muscle tissue [Na+] was not associated with inflammation, cytokine production or hypertension as reported by others. Muscle transporter adaptations in 0K- versus 1K-fed mice, assessed by immunoblot, included decreased sodium pump α2-β2 subunits, decreased K+-Cl− cotransporter isoform 3, and increased phosphorylated (p) Na+,K+,2Cl− cotransporter isoform 1 (NKCC1p), Ste20/SPS-1-related proline-alanine rich kinase (SPAKp), and oxidative stress-responsive kinase 1 (OSR1p) consistent with intracellular fluid (ICF) K+ loss and Na+ gain. Renal transporters’ adaptations, effecting a 98% reduction in K+ excretion, included two- to threefold increased phosphorylated Na+-Cl− cotransporter (NCCp), SPAKp, and OSR1p abundance, limiting Na+ delivery to epithelial Na+ channels where Na+ reabsorption drives K+ secretion; and renal K sensor Kir 4.1 abundance fell 25%. Mass balance estimations indicate that over 10 days of 0K feeding, mice lose ~48 μmol K+ into the urine and muscle shifts ~47 μmol K+ from ICF to ECF, illustrating the importance of the concerted responses during K+ deficiency.

When chronic kidney disease progresses to end stage renal disease, the optimal treatment is living kidney donation (LKD). A 10 yr prospective study of 1214 donors (PMID 27006347), reported that LKD increased risk of hypertension (HTN), by 3.64-fold, as well as HTN induced albuminuria. Our objective was to test whether a DASH-style diet (DD: 0.74% NaCl, 3%K with 1% each: Cl - , citrate, HCO 3 - ) would blunt hypertension and albuminuria following UNX vs. a western style diet (WD: 2% NaCl, 1%KCl). Uninephrectomized (UNX) male SD rats (n=5/group) preequilibrated on diets were analyzed 12-14 wks post-UNX. Systolic BP (SBP, mmHg) was similar pre-UNX in DD (126 ± 8) and WD (132 ± 8); SBP increased post-UNX by 7 ± 2 (DD) and 21 ± 5 (WD) mmHg, p=0.04. Urine injury markers (albumin, angiotensinogen, KIM-1 and plasminogen) increased in both DD and WD (all p Transporter profiles were generated from both pre-and post-UNX kidneys. Pre-UNX, DD (vs. WD) exhibited lower abundance of proximal tubule (PT) NHE3, NaPi2 and NHERF1, and higher abundance of NKA α1, NCC, NCCp, claudin 7, SPAK, ENaC subunits and AQP2 (all p < 0.01). Post-UNX (vs. pre-UNX) abundance, normalized to equivalent protein, exhibited lower claudin2, megalin, AQP1 and AQP2 in both DD and WD (all p < 0.01), and, specifically to DD post-UNX: 1.4-fold increases in NCCp, SPAKp and 0.7-fold decreases in cleaved α and γ ENaC (all p In conclusion, the phenotype of HTN and proteinuria observed following LKD in humans is evident in this pilot SD rat study. Compared to the 2% NaCl/1% KCl “Western style” diet, the 3% K + and alkali rich “DASH style diet” lowered baseline PT transporter levels, increased CLi (indicator of flow out of PT), elevated distal Na + transporters (likely due to flow from PT) and blunted the rise in BP post-UNX. The findings suggest that DASH style dietary electrolytes may improve outcomes following LKD.