Effects of herbal tea or extract on uric acid parameters in humans and rats

Uric acid kidney stones were common in Hmong‐Americans diagnosed with kidney stones in La Crosse, WI. A plant‐based tea that the Hmong use for kidney problems may affect uric acid metabolism and transport in the kidneys to alter stone formation conditions. We aim to determine effects of consumption of this tea in humans and to develop an animal model to study the effects of tea extracts on uric acid metabolism and transport. In a random order, crossover design, with tea and water (control) consumption, 24‐hour urinary uric acid (UUA) was measured in men (n=10, 20±1 years) supplied a high‐purine diet (2154 kcal, 146 gram high biological value protein). UUA in humans was 547±99 mg/day with water and 630±92 mg/day with tea consumption. Specific gravity, pH, and urine volume were also assessed. Anesthetized rats were infused with tea extract or vehicle with time 0, 30, 60, and 90 serum (SUA) and urine measurements of uric acid. We found rat SUA and UUA to be quite variable, despite control of diet, sleep‐wake cycle and surgical preparation for study. But UUA to SUA ratio may provide useful information for future extract testing. Our results, thus far, indicate that longer consumption studies and further development of an appropriate animal model to study active fractions of tea extracts are needed. Funded by the UWL Dean′s Summer Fellows program and McNair Scholars program grants.