Role of proximal tubule in the hypocalciuric response to thiazide of patients with idiopathic hypercalciuria.

ROLE OF PROXIMAL TUBULE IN THE HYPOCALCIURIC RESPONSE TO THIAZIDE OF PATIENTS WITH IDIOPATHIC HYPERCALCIURIA. Am J Physiol Renal Physiol. 2013 May 29; Authors: Bergsland KJ, Worcester EM, Coe FL Abstract The most common metabolic abnormality found in calcium (Ca) kidney stone formers is idiopathic hypercalciuria (IH). Using endogenous lithium (Li) clearance, we previously showed that in IH there is decreased proximal tubule (PT) sodium absorption, and increased delivery of Ca into the distal nephron. Distal Ca reabsorption may facilitate the formation of Randall's plaque (RP) by washdown of excess Ca through the vasa recta toward the papillary tip. Elevated Ca excretion leads to increased urinary supersaturation (SS) with respect to calcium oxalate (CaOx) and calcium phosphate (CaP), providing the driving force for stone growth on RP. Thiazide (TZ) diuretics reduce Ca excretion and prevent stone recurrence, but the mechanism in humans is unknown. We studied the effect of chronic TZ administration on renal mineral handling in 4 male IH patients using a fixed 3-meal day in the General Clinical Research Center. Each subject was studied twice: once before treatment and once after 4-7 months of daily chlorthalidone treatment. As expected, urine Ca fell with TZ, along with fraction of filtered Ca excreted. Fraction of filtered Li excreted also fell sharply with TZ, as did distal delivery of Ca. Unexpectedly, TZ lowered urine pH. Together with reduce...
Source: Am J Physiol Renal P... - Category: Urology & Nephrology Authors: Tags: Am J Physiol Renal Physiol Source Type: research