Levels of Purines in Foods and Their Metabolic Effects in Rats

Abstract

To evaluate the effects of dietary purines on purine metabolism and excretion, male Sprague-Dawley rats were fed purified amino acid diets supplemented with adenine, guanine, hypoxanthine, and xanthine at a level of 0.75 g/100 g diet. Adenine supplementation resulted in reduced growth rate, altered hepatic purine enzyme activities, and changes in purine excretion patterns in urine. Guanine, hypoxanthine, and xanthine did not affect growth rate or the patterns of purines excreted in the urine. Dietary adenine and guanine increased the concentrations of free adenine and guanine, respectively, in liver, suggesting that there was a direct incorporation of these compounds into their corresponding pools in this tissue. To determine the levels of dietary adenine supplementation needed to produce clinical symptoms and metabolic aberrations in purine metabolism, additional groups of rats were fed a semi-purified diet supplemented with graded levels of adenine during a 2-week period, and growth and renal function were monitored. Excretion of a derivative of adenine (2,8-dioxyadenine) was evident at 0.1% adenine in the diet. Increased urine volume, plasma urea nitrogen, and kidney 2,8-dioxyadenine were evident at 0.3% dietary adenine. Under the conditions of this experiment, the maximum safe level of adenine in rat diets would have to be regarded as less than 0.1%. To evaluate the levels of purines in food items ordinarily consumed in the human diet, a selection of organ meats, seafoods, and leguminous seeds were assayed for adenine, guanine, hypoxanthine, and xanthine. Wide variations in the absolute and relative levels of the four purine compounds were observed. Foods high in total purines are not necessarily high in the purines especially conducive to elevation of serum uric acid levels, i.e., adenine and hypoxanthine.