Three experiments were conducted to determine the effects of excess
dietary calcium carbonate,
phosphorus and urine acidifying and alkalizing
salts on
silica urolith formation in a model using rats fed
dextrose-based diets containing 2%
tetraethylorthosilicate (
TES). Diets containing 2%
TES lowered
weight gains to 91-95% of gains made by rats fed non-
TES diets. Urine
silica concentrations of rats fed
TES were generally in the range of 50-60 mg/dl. In experiment 1, rats fed
TES with no additional
dietary calcium carbonate had a
silica urolith incidence of 35%. With additions of 1 and 2%
calcium carbonate to the basal-
TES diet, respective urolith incidences were 45 and 60% (r = 0.99, P less than 0.02). In experiment 2, monobasic
sodium phosphate (MP) providing 0.2% additional
phosphorus resulted in a mean urine pH of 6.42 and no uroliths. Dibasic
sodium phosphate (DP) without and with 0.5%
sodium bicarbonate (SB) resulted in respective urine pH values of 6.78 and 7.14 and urolith incidences of 15 and 20% (MP less than DP and DP + SB, P less than 0.05). However, the uroliths were small averaging less than 1 mg. In experiment 3, substitution of autoclaved egg
albumin for
casein, the
protein source in experiments 1 and 2, resulted in urine pH of 7.45 and a
silica urolith incidence of 46%. An equal-molar mixture of MP and DP providing an added 0.2%
phosphorus resulted in a urine pH of 7.07 and reduced the urolith incidence to 4%, and 0.75% of dietary
ammonium chloride either with or without the added 0.2%
phosphorus gave urine acidification and complete protection from uroliths.(ABSTRACT TRUNCATED AT 250 WORDS)