The Precipitation of Polymerized Silicic Acid by Urine Protein: A Possible Mechanism in the Etiology of Silica Urolithiasis

Abstract

The precipitability of polymerized silicic acid by gelatin and urine protein was tested with solutions containing various combinations of silicic acid, protein, and salt. The ranges of pH and of the concentrations of the constituents in the mixtures were like those normally encountered in the urine of cattle on a calculogenic diet.Silicic acid precipitated in the absence of protein only at the highest concentrations of silicic acid and salt and at the highest pH. Although gelatin precipitated aged silicic acid in the absence of salt, precipitation of freshly prepared silicic acid by either urine protein or gelatin required the presence of salt. The amount of silicic acid precipitated by urine protein increased as the concentrations of the silicic acid, protein, and salt increased. There was an interaction between the effects of pH and salt, the greatest amount of precipitate tending to form at higher pH as salt concentration increased.These results suggest that urine protein, by affecting the solubility of polymerized silicic acid, contributes to the formation of siliceous urinary calculi.