ABSTRACT
BACKGROUND: Losing or donating a kidney is associated with risks of developing hypertension and albuminuria. Few studies address mechanisms or interventions. We investigate potential benefits of a K+- alkali-enriched diet and the mechanisms underlying proteinuria. METHODS: Male Sprague Dawley rats were fed either a 2% NaCl + 0.95% KCl diet (HNa-LK) or a 0.74% NaCl + 3% K+-alkali diet (HK-alk) for 3 wk prior to uninephrectomy then maintained on respective diets for 12 wk. Blood pressure (by tail-cuff), urine, blood and kidney proteins were analyzed Pre- and Post-uninephrectomy. RESULTS: Pre-uninephrectomy, HK-alk vs. HNa-LK fed rats exhibited similar blood pressures and plasma [K+], [Na+], but lower proximal (NHE3, NBCe1, NaPi2) and higher distal (NCC, ENaC, pendrin) transporter abundance, a pattern facilitating K+ and HCO3- secretion. Post-uninephrectomy, single nephron GFR rose 50% and Li+ clearance doubled with both diets; in HK-alk vs HNa-LK: the rise in blood pressure was less and ammoniagenesis was lower, abundance of proximal tubule transporters remained lower, ENaC-α fell and NCCp rose consistent with K+ conservation. Post-uninephrectomy, independent of diet, albuminuria increased 8-fold and abundance of endocytic receptors was reduced (megalin by 44%, dab2 by 25-35%) and KIM-1 was increased. CONCLUSIONS: The K-alkali-enriched diet blunted post-uninephrectomy hypertension and facilitated acid clearance by suppressing proximal Na+ transporters and increasing K+ -alkali secretion. Further, uninephrectomy associated proteinuria could be attributed, at least in part, to elevated SNGFR coupled to downregulation of megalin which reduced fractional protein endocytosis and Vmax.
