DIURNAL VARIATION OF URINARY PH

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The most invariant feature found among uric acid stone formers is an abnormally low urinary pH (<5.5). Intermittently, such values are detected in non stone formers, however, cyclical variation in pH that occur in a circadian pattern appear to protect normal subjects from nephrolithiasis. Preliminary stuies suggest that uric acid stone formers maintain a persistently low urine pH, without dirunal fluctuations, and because of this environment are predisposed to uric acid precipitation. Hypotheses: 1) There is a circadian variation in urine pH, and plasma and urinary acid-base parameters in normal subjects. 2) Part of the dirunal variation is ude to gastric secretion. 3) This circadian profile is altered in uric acid stone formers. The hypotheses will be tested by achieving the following objectives: 1) define whether cyclic variation in urine pH and plasma/urine acid base parameters status exists in normal subjects and whether it differs in uric acid stone formers. 2) explore if the diurnal variation is due to gastric acid secretion and thus modified by the administration of a proton pump inhibitor, both in normal subjects and uric acid stone formers.