Physiological chemistry of uric acid: Solubility, colloid and ion-binding properties

Abstract

1. 1. In vitro, interactions between common cations (Na +, K +, NH + 4, Ca 2+ and Mg 2+) and excess uric acid were examined. 2. 2. Each of these cations reduced the solubility of uric acid over time; the reductions produced by NH + 4, Ca 2+ and Mg 2+ were most rapid and complete. 3. 3. Each of these five cations became incorporated into excess, undissolved uric acid. These ion incorporations apparently did not result in monobasic urate salt formation; the reasons are discussed. 4. 4. Na + and K + exhibit competition for inclusion into excess undissolved uric acid; K + can displace Na + from uric acid in protein free systems, but not when 1% avian plasma is included in the buffer. 5. 5. Under a variety of circumstances, the excess uric acid can be transformed from angular crystals into small spheres or needles. The spheres are similar to those present in avian and reptilian urine, insect fat body and snail kidney. 6. 6. The presence of avian plasma proteins can alter both the final structural form of excess uric acid and the extent to which it can include cations.