H+-ATPase B-subunit Dysfunction and Calcium Nephrolithiasis
We will perform genotype and phenotype characterization of calcium stone formers and non-stone formers from several large kidney stone practices in Dallas, Milwaukee and Bern.
DNA from oral mouthwash or blood will be sent to the PI[Right Quote]s laboratory and the exons along with flanking introns of the B1 subunit will be sequenced directly using an existing protocol (Cell/DNA Repository for Disorders of Mineral Metabolism IRB# 1201-633). Phenotypic information will be sent directly to the PI. This will include:
* Plasma complete metabolic panel, magnesium, phosphorus, uric acid
* Urinary (fasting urine and 24 hr urine) stone risk (pH, Ca, citrate, oxalate, P, uric acid, Na, K, chloride, sulfate, magnesium, ammonia, volume) on random diet and restricted calcium diet (if available) *
* Bone mineral density (BMD) test of the spine, hip and forearm
* Stone analysis or radiographic data (when available)
* Stone registries in UTSW Center of Mineral Metabolism and Inselspital Bern have 24 hr urine collection on ad lib and calcium restricted diet.
We will define the phenotypic burden of heterozygosity in Aim 2 regardless of whether the subjects are stone formers or not. Aim 1 provides a genetic screen to identify the heterozygotes and cursory clinical phenotyping with outpatient data to provide a general idea. We will select heterozygous individuals (both stone formers and non-stone formers) from the Dallas cohort and do detailed metabolic studies.
Subjects will be placed on a metabolic diet for six days.
Study Day 5
* Urine: Subjects will be asked to collect their urine from day 4 -5. Subjects will be asked to collect another 24-hr urine from day 5-6.
* CT Scan: An abdominal CT scan will be performed only in normal subjects to look for possible asymptomatic occult stones.
Study Day 6
* Urine: Subjects will collect a 2-hour fasting urine.
* Blood: Approximately 1 teaspoon of blood will be drawn.
* Ammonium Chloride Load: Subjects have an oral ammonium chloride load to test for gradient defects.
Study Day 7
* Bicarbonate Infusion: Subjects will have an IV bicarbonate infusion to test for flux defects.
• Kidney stone patients: Participation in “Medical Evaluation and Treatment of Nephrolithiasis; IRB# 112006-029” and “Cell/DNA Repository for Disorders of Mineral Metabolism; IRB# 1201-633”; age >21 years or age, of either gender and any race from Dallas (n=2,000)
• Normal volunteers: Participation in “Cell/DNA Repository for Disorders of Mineral Metabolism; IRB# 1201-633”; >21 years or age, of either gender and any race with no known history of stone disease from Dallas (n=1,800); Spanish-speaking subjects will be eligible to participate in both aims.
Aim 2: Heterozygous for mutant B1; Calcium stone-formers (n=40) or normal volunteers (n=10) from Dallas who completed Aim 1