Renal potassium excretion is reduced in children with idiopathic hypercalciuria
Rodríguez-Soriano, J.; Ubetagoyena, M.; Vallo, A.
Mineral and Electrolyte Metabolism 17(6): 357-361
1991
ISSN/ISBN: 0378-0392 PMID: 1823384 Document Number: 373684
Increased luminal calcium decreases potassium secretion in microperfused rat distal tubule. To determine if such an effect is also present in vivo, we evaluated renal potassium excretion in 49 children with idiopathic hypercalciuria (urinary excretion of Ca = 5.5 .+-. 1.3 mg/kg/day) and in 214 age-matched control children (urinary excretion of CA = 1.9 .+-. 0.3 mg/kg/day). In comparison to controls, hypercalciuric children had significantly increased levels of sodium extraction (fractional excretion of Na = 0.7 .+-. 0.3. vs. 0.6 .+-. 0.3%, respectively; p < 0.001) and decreased levels of fractional potassium excretion (7.2 .+-. 2.9 vs. 9.2 .+-. 3.4%, respectively; p < 0.001), urinary potassium concentration/urinary sodium concentration (0.4 .+-. 0.2 vs. 0.6 .+-. 1.0, respectively; p < 0.001) and of the transtubular potassium concentration gradient (4.2 .+-. 1.5 vs. 5.9 .+-. 1.5, respectively; p < 0.001). All indices of potassium excretion correlated significantly and inversely with urinary calcium excretion (p < 0.001). After an oral calcium load, performed in 30 hypercalciuric children, the increased rates of urinary calcium excretion were accompanied by increase rates of urinary sodium excretion and by a significant decrease in the transtubular potassium concentration gradient. These results support the hypothesis that increased luminal calcium concentration also inhibits renal potassium secretion in man.